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MODERN METHODS OF WELDING 



MODERN 
METHODS OF WELDING 

AS APPLIED TO 

WORKSHOP PRACTICE 

DESCRIBING VARIOUS METHODS 



OXY-ACETYLENE WELDING 
OXY-HYDROGEN WELDING 
LEAD BURNING 
THERMIT WELDING 
ELECTRIC ARC WELDING 
ELECTRIC BUTT WELDING 



ELECTRIC SEAM WELDING 
ELECTRIC SPOT WELDING 
MIRROR WELDING 
CUTTING IRON AND STEEL 
EYE-PROTECTION IN WELD- 
ING OPERATIONS 



AMERICAN METHODS 



j/h. 



BV 



DA VIES 



LEEDS TECHNICAL SCHOOL AND CONSULTING ENGINEER 




NEW YORK 
D. VAN NOSTRAND COMPANY 

Eight Warren Street 
1922 



"is 2,2,7 



PRINTED IN GREXT BRITAIN BY BILLING AND S'dNS, LTD. 
GUILDFORD AND ESHER 



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01 

CO 

PREFACE 

We live in a world of wonders. The life of each one of us is, of 
necessity, so hemmed in by circumstances that none can see much 
beyond the bounds of his own habitat. We recognise the progress 
of an industry which comes within our own experience, but we know 
little of those with which we are not in personal contact. 

The pressman who clamps the plates on a modern lightning news- 
paper press does not see anything very startling or interesting in the 
work. The man who pulls levers in the pulpit of a great steelworks 
is not apt to realise that there has been a marvellous advance in the 
realm of manufacture. The attendant on a bottle-blowing machine 
has learned to take his work as a matter of course. It is found 
through the entire list of trades and occupations. 

Yet each of these men is at times impressed by the remarkable 
advances made in some industry other than his own, because such 
knowledge comes to him, as it were, suddenly, not by the almost 
imperceptible movement which marks progress in work that is 
familiar. 

The means which have brought about industrial development 
are worth studying. No armed warrior ever sprang full-grown 
from his cradle; no giant industry has ever come into being in a 
year or decade. It takes time to develop the machinery and acquaint 
the world with the advantages of a new aid to manufacture, to 
commerce, to civilisation, or to human comfort. He who reads this 
book can hardly fail to be impressed with the idea that no man 
can measure the possibilities of industrial growth. Who can say 
that at the close of the twentieth century " Darkest Africa " may 
not be under-selling us in our home markets? Who can be sure that 
with the development of China and the East, there may not come 
supremacy in industry before which our light shall pale ? To-day 
the industry is exceptional in which there has not been an entire 
alteration and renewal in the machinery within the last few years. 

The tale of manufacturing progress is one not half told, one which 
never can be told in full, because it grows faster than the ability 



vi PREFACE 

to record its development. In every vocation, in every city of the 
globe, are geniuses studying how to advance the lines of work in which 
they are engaged. Every year the standards that win success are 
set higher, yet every year witnesses increasing gains and greater 
triumphs. 

Electricity is believed to pervade the universe. Astronomers 
see evidence of its action in the sun, in the stars, in the comets. 
Its properties are so varied, it affects substances so differently, 
that it is safe to say that we have as yet learned but a fraction of 
what mankind is destined to know about this wonderful thing. 
Because it so readily lends itself to the transmission of energy, we 
think of it as a source of power, whereas really it is but a means of 
transmitting power, like the endless leather belts commonly used 
for driving machinery. 

The man who thinks he will read up a little on electricity is some- 
times very much disappointed because he cannot learn at the out- 
set, in a little primer, just what electricity is, and so advance step 
by step to a full knowledge of the subject. But there is no help for 
it. The operator of electricity to-day must begin, as did those who 
came before him, at the other end of the problem, and learn how 
electricity acts and what it does. After a time he will acquire a 
notion of things which will satisfy his craving for knowledge, and 
will cease to bother much about the theory. 

Operators and others who follow the instructions in this book will 
soon be convinced of the great importance of welding processes to 
the future manufacturing and industrial world. It is the simplest 
possible axiom, when we stop to think (though few people ever do 
stop to think), that the only way in the long run for labour as a 
whole to get more wealth is for it to create more wealth ; the only 
way to create more wealth is to increase productivity of labour. 

The field for the further application of welding is enormous; 
but this further application is being delayed by lack of com- 
plete knowledge of the art, the utterly confusing, and, in many 
cases, diametrically opposed claims of competing interests. There 
is needed a cultivation of the co-operation spirit which will permit 
a frank, open discussion of the merits of the different processes, 
so that a reasonable agreement as to those merits may be reached. 
If there are prospective users of welding who are in doubt as to 
whether they should use gas or electric welding, or neither, can it be 
supposed that their confidence in any process will be enhanced by 
hearing its advocates claim that it is the only safe and economical 
one ? I am not setting forth impracticable ideals, but rather 



PREFACE vii 

common-sense principles, already found successful in many business 
fields, the application of which is bound to yield the best results 
for all concerned. 

It would be difficult to suggest a branch of the applied arts which 
has advanced more rapidly in recent years than that of electric and 
oxy-acetylene welding. Both processes gained status in the war; 
and, although some of the more extreme manifestations of their 
possibilities which the war encouraged are little likely to be paralleled 
in the early days of peace, the methods have now won for themselves 
a definite place in the shop routine. They have established their 
ability to tackle certain classes of work in an economical and satis- 
factory way. That both methods are destined to advance in useful- 
ness, alike in extension and intension, there is no question; and, 
although they are in the hands of specialist firms, the general shop 
manager of the not far distant future is likely to find that he is 
expected to be able to apply them. Moreover, not only the manager, 
but others, both the engineers and the " semi-skilled," are likely to 
find interest and profit in these processes. There is probably no 
other recent improvement in applied mechanics which has received 
the scientific study devoted to autogenous welding. The result is 
that its practice has become an art to which one must give intelligent 
and well-directed study if one would avail oneself of its uses. 

The universal application of this process, in every branch of 
industry where metals are employed, makes inevitable a great de- 
mand for capable operators. It is to the advantage of all concerned 
that operators should understand their work and their tools, that 
they should be able to apply intelligently the principles involved. 



INTRODUCTION 

In presenting this book to the welding industry, I may say that I 
have devoted my whole time to the welding processes and the 
materials used, and they are all concisely described in their various 
chapters. If the readers will give attention to the following pages, 
they will find many points that will help them in their studies and 
guide them to a knowledge of the processes. In the course of 
eighteen years' experience of the welding industry I have found that 
such a book as the present is badly needed. I now make an en- 
deavour to supply the deficiency. It is my desire to do all in my 
power to raise the status of welders in this country; and this will 
be best achieved if they can be induced to pursue a course which 
will make them proficient. 

Some time ago an effort was made to establish a system of certifi- 
cates of proficiency for operators, but unity between the associa- 
tions interested is not yet sufficient to allow this. 

In the comparatively limited space available for my purpose, 
I have attempted to give a clear and consecutive description of the 
principles upon which an industry of unsurpassed importance is 
based. With the object of accomplishing my task, however, in a 
manner at once agreeable and instructive, I have now and again 
departed from the general plan to dwell on some particular point. 

While sensible of the defects in my book, I venture to hope that 
to those practically engaged or interested in the conduct of numerous 
processes covered by its title it may prove to be of service. 

I take this opportunity of acknowledging my gratitude for 
assistance from Messrs. British Oxygen Company, Ltd., Messrs. 
Charles Bingham and Company, Ltd., Messrs. Leeds and Butter- 
field, Messrs. British Insulated and Helsby Cables, Ltd., and H. M. 
Hobart, President of the American Welding Society. 



CONTENTS 

CHAPTER PAGES 

PREFACE ------- V 

INTRODUCTION ------ ix 

I. WELDING IN GENERAL ----- 1-5 

Concise description. Articles welded. 

II. LEAD BURNING - - - - - - 6-12 

Description of the gases. Samples of welds. 

III. MANUFACTURE OF OXYGEN - - - - 13-16 

Describing Brin process. Linde liquid air. Process described. 

IV. MANUFACTURE OF HYDROGEN - - - - 17-21 

Description of process. General details. 

V. MANUFACTURE OF CARBIDE ... - 22-26 

History. Starting-point of the acetylene industry. Principal 
materials for carbide. 

VI. ACETYLENE ...... 27-34 

Physical properties. Weight of water to weight of carbide. 
Impurities. Purifying materials. 

VII. OXYGEN CYLINDERS ----- 35-39 

Manufacture of cylinders. Regulations. 

VIII. ACETYLENE GENERATORS - - - - - 40-45 

General construction. Polymerisation. Working of generator 
described. General rules. 

IX. OXYGEN REGULATORS ----- 46-48 

Description of regulator. Special coupling. 

X. REGULATIONS ------ 49-51 

Regulations for generators. 

XI. BLOWPIPES ...... 52-64 

Pattern and consumption. Series of blowpipes. Testing the 
gases. General rules. 

XII. FLEXIBLE TUBING ..... 65-66 

Quality of rubber tubing. 



xii CONTENTS 

CHAPTER PAGES 

XIII. SAFETY VALVES ..... 67-71 

Descriptive notes. Choice of safety valve. 

XIV. PURIFIERS ...... 72-77 

Remarks on design. Testing the purifier. The Keppler test. 

XV. SELECTION AND INSTALLATION - - - 78-82 

Generators described. Conditions a generator should fulfil. 
Order of installation. 

XVI. METHODS OF WELDING .... 83-92 

Preparations prior to welding. What causes adhesion. 
Test-pieces for operators. 

XVII. PREPARATION OF WELDS .... 93-99 

Bevelling. Defective welding illustrated. Phenomenon of 
expansion. 

XVIII. WELDING TABLES ..... 100-103 

Construction. Illustration of canting tables. 

XIX. FURNACES FOR HEATING ... - 104-108 

Description of furnace. Best method of preheating. 
Expansion and contraction. 

XX. IRON AND STEEL ----- 109-119 

Difference between iron and steel. Physical properties. 
Pure iron. Interposition of oxide. 

XXI. CAST IRON ------ 120-L31 

The strength and solidity. Action on cooling. White and 
grey iron. Difficulties of expansion. 

XXII. DISSOLVED ACETYLENE ... - 132-134 

Brief description. Regulations. Correct tip of flame. 

XXIII. CUTTING IRON AND STEEL ... - 135-153 

Illustration of cutter. Oxidation of iron and steel under 
oxygen. Heat value of carbo -hydrogen. 

XXIV. THERMIT WELDING ----- 154-159 

Preparation. Thermit required for welding. Composition 
of thermit. 

XXV. PROPERTIES OF PRINCIPAL NON-FERROUS METALS - 160-163 
Important properties. Table of melting-points. 

XXVI. DELTA METALS ..... 164-167 

Table of metals. Important to operators. 

XXVII. ALUMINIUM - - - - - -168-176 

Comparative cost. Melting-points of the metal and its 
oxide. Alloy mixture. Points on welding. 

xxviii. copper ...... 177-183 

Principal varieties. Special welding-rods. Failures in 
welding. 



CONTENTS xiii 

CHAPTER PAGES 

XXIX. BRONZE ------ 184-186 

Bronze welding. Power of the blowpipe. 

XXX. BRASS .--... 187-190 

Physical properties. Melting-points. 

XXXI. AMERICAN METHODS - 191-199 

Description of what is being done. Welding machines. 
Medium-pressure generator. Cutting machines. Non- 
flash blowpipe. 

XXXII. THE METALLURGY OF ARC WELDING - - 200-205 

Metallurgy of steel. Gas-holes in electric welds. Im- 
purities. 

XXXIII. BRIEF DESCRIPTION OF ELECTRIC WELDING - 206-210 

Spot, butt, seam arc detailed. Relative cost. Rivets 
versus welds. 

XXXIV. ELECTRIC ARC WELDING ... - 211-226 

General processes. Quasi-arc process. Welding with 
metallic electrodes. Practical notes. 

XXXV. SPOT WELDING ----- 227-235 

Sheets to be welded. Articles that can be spot welded. 

XXXVI. ELECTRIC BUTT WELDING - - - - 236-243 

Butt- welding processes. Electric current no effect on 
weld. Chain welding. 

XXXVII. ELECTRIC SEAM WELDING - - - - 244-246 

Welding sheet brass. Working operation. 

XXXVIII. EYE-PROTECTION IN IRON WELDING OPERATIONS - 247-257 
Remarks on types of glass. Proper selection of colour. 
Summarising. 

XXXIX. MIRROR WELDING ----- 258-263 
Describing the process. Showing how mirror welding can 
be accomplished. Welding a boiler. 



LIST OF ILLUSTRATIONS 

FIG. PAGE 

1. CUTTING BOILER FLANGES AUTOMATICALLY WITH A " RADIOGRAPH " - 5 

2. INJECTOR BLOWPIPE ....... 7 

3. SHOULDER TAPS FOR USE WITH LEAD-BURNING BLOWPIPE - - 7 

4. OXYGEN REGULATOR ....... 8 

5. LEAD-BURNED JOINT ....... 9 

6. LEAD- BURNED JOINT ....... 9 

7. MOULDING TOOL FOR HEAVY VERTICAL WELDING - * - - 10 

8. 4,000-UNIT GENERATORS FOR PRODUCING OXYGEN AND HYDROGEN - 20 

9. SECTION OF AN OXYGEN CYLINDER - - - - - 39 

10. 10-CWT. CARBIDE-TO-WATER GENERATOR - - - - 42 

11. DAVIS - BOURNONVILLE 50 POUNDS CAPACITY MEDIUM - PRESSURE 

GENERATOR ........ 43 

12. DAVIS - BOURNONVILLE 100 POUNDS CAPACITY MEDIUM-PRESSURE 

GENERATOR ----.... 44 

13. OXYGEN REGULATORS: 1 TWO GAUGES, 1 ONE GAUGE, 1 NO GAUGE - 46 

14. DOUBLE CYLINDER CONNECTOR - - - - - - 47 

15. AIRTIGHT CARBIDE CHAMBER, " ATOX " TYPE - - - - 50 

16. FOUCHE BLOWPIPE, SECTION AND ELEVATION - - - 52 

17. UNIVERSAL TYPE BLOWPIPE, HEAD AT SPECIAL ANGLE - - 53 

18. UNIVERSAL SINGLE TYPE BLOWPIPE - - - - 53 

19. UNIVERSAL MULTIPLE TYPE BLOWPIPE, SMALL SIZE - - 54 

20. UNIVERSAL MULTIPLE TYPE BLOWPIPE, LARGE SIZE - - - 54 

21. ENDAZZLE BLOWPIPE, SINGLE TIP PATTERN - - - - 55 

22. ENDAZZLE BLOWPIPE, MULTIPLE TIP PATTERN - - - - 56 

23. OSBORNE BLOWPIPES, FOUR DIFFERENT TYPES - - - - 57 

24. DAVIS-BOURNONVILLE SMALL SET OF INTERCHANGEABLE TIPS- - 58 

25. DAVIS-BOURNONVILLE LARGE SET OF INTERCHANGEABLE TIPS - - 59 

26. SHOWING THE CORRECT NEUTRAL FLAME - - - - 63 

27. SAFETY VALVE, ELEVATION AND SECTION - - - - 68 

28. STANDARD SECTIONAL TYPE SAFETY VALVE - - - - 69 

29. PURIFIER, SHOWING SECTION AND ELEVATION WITH PURIFYING MATERIAL 74 

30. " ATOX " PURIFIER - - - - - - - 75 

31. BUTT JOINT ....---- 85 

32. INDENTS, NOT SUFFICIENT WELDING-ROD ON - - - - 85 

XV 



XVI 



LIST OF ILLUSTRATIONS 



FIG. 

33. ROUND BAB BEVEL, CHISEL POINTS 

34. TUBE BEVEL ...... 

35. FRACTURE AFTER BENDING .... 

36. LACK OE PENETRATION ----- 

37. SINGLE BEVELLED JOINT .... 

38. ADHESION, BAD WELD ..... 

39. NOT FULLY PENETRATED, FIRST STARTING OF FRACTURE 

40. NOT PENETRATED THROUGH .... 

41. BENDING A TEST- PIECE IN A VICE 

42. FLAT BAR DOUBLE BEVEL .... 

43. ANGLE IRON, BEVELLED ONE SIDE 

44. NOT PENETRATED ..... 

45. SPACE SHOWN UNWELDED .... 

46. MACHINE OPERATOR WELDING SEAMS 116 INCHES LONG 

47. CASTING BROKEN, SET AND CRAMPED, AND WELDED - 

48. PROPER SET FOR WELDING PIPES ... 

49. WELDED CROSS IN PIPE .... 

50. SHOWING CONSTRUCTION OF PIPE 

51. SHOWING PIPE AT 45 DEGREES, WELD AND BEVEL 

52. MILD STEEL OPERATOR'S TABLE - - - 

53. ADJUSTABLE WELDING TABLE WITH VICE ATTACHMENT 

54. OPERATING TABLE WITH FIRE-BRICKS 

55. TABLE FOR A NUMBER OF OPERATORS - 

56. TILTING TABLE ...... 

57- A KEROSENE PREHEATING TORCH 

58. GAS-HEATED PREHEATING OVEN - - - - 

59. ASBESTOS SCREEN FOR COVERING CASTINGS 

60. LIGHT LIFTING CRANE - - , . 

61. TENSIONAL TESTS - - - - 

62. CAST-STEEL TRAMWAY GEAR CASE WELDED 

63. CAST-IRON PRESS SIDE BROKEN - - - - 

64. CAST-IRON PRESS SIDE WELDED 

65. TWO-CYLINDER MOTOR ENGINE BROKEN 

66. TWO-CYLINDER MOTOR ENGINE WELDED 

67. BROKEN WATER PUMP ..... 

68. PERFECT NEUTRAL FLAME .... 

69. HAND-CUTTING BLOWPIPE .... 

70. THE " RADIOGRAPH " CUTTING STEEL PLATE 

71. COUPLED CYLINDERS, FOR CONTINUOUS WORK - 

72. CUTTING ROUND THE FLANGE OF THE END OF A BOILER 

73. CIRCULAR CUTS IN STEEL PLATES 2£ INCHES THICK 

74. CUTTING A CAST-STEEL TURBINE ROTOR 9 INCHES THICK 

75. FELLING A STACK WITH AN OXYGEN CUTTER 



87 

87 
88 
88 
89 
89 
90 
90 
91 
94 
94 
95 
95 
96 
97 
98 
98 
98 
98 
100 
101 
102 
102 
103 
104 
105 
106 
107 
117 
121 
122 
122 
129 
130 
131 
133 
136 
139 
140 
141 
142 
144 
146 



LIST OF ILLUSTRATIONS 



xvn 



FIG. 

76. 

77. 
78. 
79. 
80. 
81. 
82. 
83. 
84. 
83. 
86. 
87. 



90. 

91. 

92. 

93. 

94. 

95. 

96. 

97. 

98. 

99. 
100. 
101 

02. 
103. 
104. 
105. 
106. 
107. 
108. 
109. 
110. 
111. 
112. 
113. 
114. 
115. 
116. 
117. 
118. 



PAGE 

THE lA OXYGRAPH, AUTOMATIC PANTOGRAPH CUTTING MACHINE - 147 

OXYGRAPH TRACER WHEEL, SWIVEL STANDARD .... 148 

OXYGRAPH MACHINE CUTTING TORCH WITH MOTOR CONTROL SWITCH - 149 

SMALL SOLID END CONNECTING-ROD AND BILLET - - - 150 

LEATHER- CUTTING PUNCH FOR SHOE MANUFACTURE - - - 150 

WRENCH TRIMMING DIE ROUGHED OUT ON OXYGRAPH - - - 151 

VIEWS OF THREE DIES CUT FROM 110-POINT CARBON STEEL - - 152 

NEW TEETH PUT IN WHEEL BY " THERMIT " WELDING - - 154 

THERMIT- WELDED LOCO FRAME - - - - - - 155 

THERMIT-WELDED ROCK CRUSHER - - - - - 158 

FRACTURED ALUMINIUM GEAR CASE - - - - - 171 

FRACTURED ALUMINIUM- ALLOY GEAR CASE - - - - 175 

ALUMINIUM- ALLOY GEAR CASE REPAIRED - - - - 176 

SECTION OF A COPPER WELD - - - - - - 179 

MICROPHOTOGRAPHS FROM THE REGION OF A WELD - - - 182 

THE DUOGRAPH WELDING MACHINE ..... 192 

SHOWING DIFFERENT OPERATIONS OF THE DUOGRAPH - - - 193 

MEDIUM-PRESSURE GENERATOR, 200 POUNDS CAPACITY - - - 195 

PART SECTION, NON-FLASH BLOWPIPE ..... 196 

AIR-GAS PREHEATING TORCH - - • - - - 197 

WELDING TORCH TIP DIRECTLY ON METAL .... 197 

WELDING TORCH TIP DIRECTLY AGAINST BRICK - - - 198 

DRILLING A HOLE THROUGH 5-INCH AXLE - - - - 199 

SHOWING AREAS AT HIGH MAGNIFICATION - - - - 201 

SHOWING AREAS AT HIGH MAGNIFICATION .... 201 

ELECTROLYTIC IRON ....--- 202 

ELECTROLYTIC IRON NITROGENISED BY ANNEALING - - - 202 

EDGE OF WELD MADE WITH COVERED ELECTRODE - - - 203 

UNANNEALED WELD SECTION ...... 203 

ADHESION IN WELD ....... 204 

SLAG ENCLOSED IN WELD ...... 204 

USE OF METAL ELECTRODE IN WELDING STEEL BANDS - - 217 

USE OF CARBON ELECTRODE WITH METAL FILLER - - - 218 

SEAM PREPARED FOR HAND WELDING WITH CARBON ELECTRODE - 219 

COMPLETE UNIT FOR ELECTRIC ARC WELDING - - - - 221 

AUXILIARY PANEL ....... 222 

PRESCOT SPOT WELDER ------- 230 

SPOT-WELD FLAT BARS TO CORRUGATED SHEETS - - - 231 

PIECE OF ANGLE IRON TO FLAT PLATE - - - - - 231 

ROUND IRON TO ANGLE IRON ...... 232 

BUTT-WELDING TOOL STEEL ...--- 239 

FLASH AND UPSET WELD ...... 240 

PRESCOT BUTT WELDER ------- 241 



xviii LIST OF ILLUSTRATIONS 

FIG. PAGE 

119. BUTT WELDER MAKING CHAINS - - 242 

120. ELECTRIC SEAM-WELDING MACHINE ----- 245 

121. SPECTRUM OF A MAZDA LAMP ---.._ 248 

122. PFUND GOLD GLASS GOGGLES ----._ 248 

123. POPULAR FORM OF HELMET WITH CIRCULAR WINDOW - - - 249 

124. WELDER'S HAND SHIELD ...... 250 

125. ALUMINIUM HELMET, FRONT AND BACK VIEWS - - - . 251 

126. SUNDRY SPECTRA 6 ...... 252 

127. SUNDRY SPECTRA 7 ...... 253 

128. FIBRE GOGGLES -------. 254 

129. TWO PAIRS OF GOGGLES FITTED WITH ESSENTIALITE AMBER LENSES - 257 

130. PRINCIPLE OF MIRROR WELDING ..... 259 

131. MIRROR WELDING AS APPLIED TO THE PIPES .... 260 

132. INTERNAL WELDING OF A BOILER ..... 261 



MODERN 
METHODS OF WELDING 



CHAPTER I 
WELDING IN GENERAL 

It is well known to everyone who takes an interest in welding and 
welding processes that the existing opinion as to the value of the 
processes and the practical results obtained is in a state of uncer- 
tainty. The chief ground for this uncertainty lies in the fact that 
these new processes have only been introduced recently into indus- 
trial practice, and rest entirely on an empirical basis. Although 
oxy- acetylene welding is now extensively used, and is of great 
theoretical and practical interest, it has never been made the object 
of systematic and exhaustive research. 

The author has had eighteen years' experience of welding, and has 
made exhaustive tests and long studies, not only of what is being 
done in this country, but also of the progress made in the United 
States and Germany. The latter country is far more advanced 
than Great Britain. The Germans have carried out systematic 
and exhaustive researches. Their operators are scientifically 
trained, are taught metallurgy and chemistry, including the chemi- 
cal compositions and melting-points of all metals and oxides, make 
test-pieces for experimenting with the chemical and mechanical 
tests, and employ microscopic and macroscopic examinations, both 
of the melted zone and the neighbouring parts. Their welding, as 
a rule, is very neat, as they are not allowed to execute commercial 
work until they have become fully proficient. 

The introduction of oxy-acetylene welding has opened up an 
enormous field, in which any metal can be dealt with, and such an 
article as a cracked motor frame or cylinder can be rapidly welded. 
In these directions there seems to be ample scope for the applica- 
tion of engineering skill, and recent developments have shown that 
it is difficult to put a limit to the purpose to which engineers may 
yet apply the process. 

To-day the business has grown beyond the limits of personal 
supervision. The necessity for organised instruction of operators 
is becoming more and more obvious in the interest of both work- 

l 



2 MODERN METHODS OF WELDING 

men and employer. Several welding schools have now been started 
in various centres about the country, whence a stream of qualified 
welders is already beginning to flow to the workshops, where most 
of them are able to turn their training to practical use. 

They teach the operator under practical conditions the right 
flame for different work, the principles on which the blowpipe is 
constructed, the way to handle it, and a variety of technical 
and theoretical points, which are always useful to him in his sub- 
sequent career. He is also taught thoroughly the construction, 
working, and maintenance of the plant. 

It is the operator of to-day, well instructed in the points, whom 
we hope to find the professional welder of to-morrow. The time 
is not far off when employers will refuse to engage a welder unless 
he can produce the certificate of proficiency. This cannot be 
obtained unless the operator possesses thorough knowledge and 
practical experience of the process. 

The author has undertaken many investigations in this process. 
The oxy-acetylene method, when properly worked, possesses 
numerous marked advantages. In the first place, the operating 
flame can easily be controlled, and the temperature attained at 
various zones can be readily regulated. Secondly, the work can 
be easily accomplished, owing to the high temperatures reached 
(3,600° C), and the appliances are convenient to handle and reliable 
in operation. 

The most important conditions for securing good results are — 

1. The use of the purest acetylene possible. 

2. The use of a blowpipe so designed as to ensure accurate 
adjustment in the proportion of the mixed gases and to secure their 
exit at a velocity capable of keeping the metal sufficiently fluid 
without the melting flame being too rigid. 

3. The use of an absolutely pure welding-rod. 

4. The provision of an absolute neutral zone in the melting flame, 
neither oxidising nor reducing. 

5. The edges must be free from all impurities, and, if over 
-£$ inch thick, must be bevelled. 

6. The use of deoxidising agents eliminating the oxides, in view 
of unavoidable oxidation of the metal subject to the melting process. 
It is necessary to bear in mind the relation between the melting- 
points of the oxides and of the metal itself, which is a most important 
matter. 

7. Rapidity in melting, in order to avoid excessive heating, 
which not only alters and deteriorates the original structure of 



WELDING IN GENERAL , 3 

the metal, but would even favour the occlusion of the gases (particu- 
larly hydrogen) and so occasion the formation of blowholes in the 
melted zone. 

In addition to these considerations, care should be taken that 
no sudden cooling occurs. The conditions may have to be modified 
on account of the conductivity and special dilation of the material, 
as well as in relation to the thickness, size, and shape of pieces 
operated upon. 

Eor those who are familiar with this process of welding and cut- 
ting it is not difficult to appreciate its varied applications. The 
ease and rapidity with which experienced welders can carry out 
repairs in situ, and the portability of the plants, make the process 
valuable, if not indispensable. The service rendered by it in many 
workshops, where the welding of articles of all kinds is a daily 
necessity, is calculable. 

The oxy-acetylene process occupies a leading place in all aero- 
plane and airship industries. It is used with advantage in welding 
sheet steel stampings, cylinders, aluminium crank cases and 
machinery parts, steel tubes, stamped steel water-jackets for cylin- 
ders, broken cast iron. Moreover, for cutting iron and steel this 
process has no rival whatever. It will cut wrought iron or steel 
plate 20 inches thick. The flame has been applied to the case- 
hardening of steel, and some firms are using this on a large scale. 
It is well known that the flame containing an excess of acetylene 
is a very energetic carboniser. 

This process may be employed on any class of work. It will weld 
30-gauge steel or lj-inch boiler plates, cut mild steel up to 20 inches 
thick; weld any commercial metal, such as cast iron, aluminium, 
copper, bronze, zinc, lead, delta metal. In the repair of broken 
machinery and parts it is always above its rivals; repairs are exe- 
cuted quickly and can be done without dismantling in many cases. 
It can be used in the manufacture of safes and tanks, in the jointing 
of pipes, steam superheaters, casks, artistic ironwork, in adding 
metal to parts worn by friction, filling up holes or parts of new 
structure cut away in error, welding of tool steel to wrought- 
iron bars, and welding of copper or brass tubes. The flame can be 
used for preheating and for hammering and annealing after welding, 
thereby ensuring a soft metal, a method not practicable in the electric 
process. 

In the welding of light sheet steels with 24-gauge metal, 45 feet 
per hour can be welded, with a consumption of only 4 feet of oxygen 
and 3 feet of acetylene. On the other hand, when the metal reaches 



4 MODERN METHODS OP WELDING 

| inch thick, electric welding has the advantage both in speed and 
cost. 

When the process of acetylene welding was first introduced, its 
apparent simplicity led many engineers wrongly to assume that 
welding appliances might be regarded as general workshop tools, 
which any inexperienced but handy man could operate with success. 
Consequently much work was condemned wholesale because of the 
defects in the weld. The author would emphasise that this is not 
the fault of the process, but of inefficient workmen. 

It is estimated that there were, during the recent war, 33,000 
employed in this country in welding processes, of whom 25,000 
entered the field during the war. Of the total number, 90 per cent, 
are not fully skilled — that is, they are incapable of executing satis- 
factory welds on all metals, being mostly employed on sheet steel. 
The impetus that has been given under war conditions should stimu- 
late employers to investigate and exploit this revolutionary process, 
the possibilities of which have no obvious limits. 

In the shipbuilding trade this process can be utilised very much 
more than at present — for instance, in making knee brackets, 
stays, and frames. These can all be cut and welded by blowpipes, 
with present costs reduced 50 per cent, and output increased. 
A blowpipe only requires one man ; but an anglesmith, when welding 
a knee bracket, requires two or three assistants. Most shipyards 
have plants, but they are not utilised to advantage. 

In all Avelding it is most important that the work should be ade- 
quately prepared before commencing to weld, as all time spent in 
this way is amply repaid afterwards in the easier execution, and 
also by the homogeneous nature of the weld. It is, however, a 
subject on which it is impossible to lay down any hard-and-fast 
rules, the varying nature of the work accomplished making it im- 
possible to do so. The general principles obtained in the best prac- 
tice point out that the line of weld must be opened out — that is, 
the two edges must be bevelled to an angle of 45 degrees, to make 
certain that the weld is well penetrated, not merely sealed over, and 
to strengthen the weld by increasing the surface of contact. 

One of the most important things to do in the preparation is to 
arrange the pieces to be welded in such a position that there shall 
be no deformation, breaks, or cracks, or internal strains, and that 
they may be linable at the conclusion of the operation. This is a 
point in which the skill and experience of the operator are revealed, 
as there are no rules to guide him, and upon any work but that of 
the simplest character failure to grasp and apply the laws of expan- 



WELDING IN GENERAL 5 

sion and contraction means the partial or total ruin of the work. 
It is impossible to control expansion and contraction by physical 
force, so the only way to prevent disastrous results is to foresee 
the probable direction and extent of the phenomena, and nullify 
the effects by preheating certain parts of the work, either by the 
blowpipe or the welder's furnace. 

It is good practice to raise the temperature to nearly red heat 
in the furnace and weld, then allow to cool slowly and uniformly 




Fig. 1. — The Radiograph, used for Circular Cutting, Automatically, as 
shown, is Cutting Annular Rings 31 Inches Diameter by 6 Inches 
Thick at a Speed of 7 Inches per Minute. 

Note the clean cut and accuracy of the rings. 

in sand or asbestos; but all cold currents of air must be avoided. 
All castings should be preheated bodily. This is a great advantage, 
for not only does it save gases, but it prevents any irregular expan- 
sion, and hence no fractures. 

The cutting of iron and steel by the oxy-acetylene flame is being 
very extensively used. This involves the use of a blowpipe of a 
different design, which provides for the oxy-acetylene flame and an 
auxiliary jet of pure oxygen to be impinged on the line of cutting. 
The principle underlying this method consists of taking advantage 
of the fact that, when heated, iron and steel can be oxidised very 
quickly by a jet of oxygen, which jet, delivered at high pressure, 
blows away the oxide that is made, leaving a narrow, clear cut, 
almost as clean as a saw cut. 



CHAPTER II 
LEAD BURNING 

This process is one of fusion of lead by oxy hydrogen, air hycrogen, 
or coal-gas hydrogen. The air-hydrogen process, dating back over 
one hundred years, for a considerable time was only employed in 
chemical work on the construction of acid tanks and vessels with 
their pipe connections. The tanks being built of wood, lined with 
sheet lead, the junction of the sheet was effected by this method. 
At a later period this system was employed in large gasworks, 
more recently for the manufacture of electric batteries and their 
plate connections. If solder had been used on either class of work, 
it would have been attacked by the acid. It was restricted on 
account of its cost. 

In the latter part of the year 1888 a series of experiments was 
carried out by the Brin's (now British) Oxygen Company, with the 
object of using coal-gas from the ordinary town main and oxygen 
from a trade cylinder. After due consideration of the matter, it 
was thought possible to utilise the pressure of the oxygen cylinder 
to obtain an injection action by which the supply of coal-gas at low 
or main pressure could be increased and thoroughly mixed with the 
oxygen in the blowpipe previous to ignition. In order to complete 
combustion (thus preventing the formation of carbon deposits on 
the melted lead), after various trials had been made, the injector 
blowpipe which we illustrate on p. 7 was designed, and was found 
eminently adapted to the purpose. It fulfilled in other respects 
all the requirements necessary to ensure good work, and, moreover, 
as it produced a flame at much higher temperature than could be 
secured by the old hydrogen-and-air system, it enabled the plumber 
to execute about double the amount of work, of better quality, and 
without assistance. 

H (Fig. 2) is the inlet for the coal-gas supply ; shows the injector 
inlet for the oxygen supply, fixed in position with the injector 
removed, showing the coned end which projects through the chamber 
into a cone formed in the body. The pipe leading away from the body 
is screwed at the end to take the nipple, which is of various sizes, to 

6 



LEAD BURNING 7 

deal with lead from the thinnest section up to J inch thick. The 
essential features of this type of blowpipe are the shape and design 
of the injector cones, with their relative position to each other; the 
reservoir for the coal supply provided between the two gas inlets 




Fig. 2. — Injector Blowpipe. 

and H; together with the mixing chamber, into which the brass pipe 
is screwed. The flame also differs somewhat from that of the old 
hydrogen type of blowpipe, its chief characteristic being a well- 
defined pale blue cone about a quarter of an inch long. The hottest 




Fig. 3. — Shoulder Taps eor Use with Lead-Burning Blowpipe. 

part is the point of the cone, which, in use, impinges on the metal 
operated upon. Melting is clean and bright. This flame is best 
controlled by the use of what are known as " shoulder taps," illus- 
trated herewith. 

These taps in Fig. 3, marked H and respectively, correspond 



8 MODERN METHODS OF WELDING 

with those on the blowpipe, and are connected by two lengths of 
rubber tubing, with the twofold object of securing flexibility and 
lightness, the pressure being previously reduced from the other 
end of the tap, marked H. A rubber tubing leads to the ordinary 
coal-gas supply from the main, and the oxygen tap, marked 0, is 
similarly connected by a rubber tube with the outlet of an 
endurance regulator, which is illustrated herewith. 

This regulator in Fig. 4 is connected by a ring nut, seen at the 
bottom, to the oxygen cylinder. The knurled nut on the right is 
screwed into the diaphragm plate, indented on the sleeve, by which 
means it can be adjusted to maintain any constant outflow of oxygen 




Fig. 4. — Oxygen Regulator. 

from the cylinder up to 30 pounds pressure per square inch. The 
projection immediately opposite is a safety valve, the outlet or stop 
valve being shown on top. These illustrations constitute a com- 
plete lead-burning outfit, with the exception of the rubber tubing 
and the oxygen cylinder. A sample injector blowpipe was submitted 
to the Gas Light and Coke Company for trial in their chemical 
works at BeCkton, and gave satisfactory results. A large order 
was consequently placed. The system has met with universal 
approval, not only in the trades already mentioned, but also for 
roof work and general plumbing. If lead burning is required where 
there is no coal-gas supply, this can be obtained compressed in 
cylinders similar to those used for oxygen ; but an endurance regula- 
tor would have to be used on the coal-gas cylinder. In lead burn- 
ing, in order to secure sound joints in any class of work, it is neces- 
sary that the joints are scraped perfectly clean and bright, and also 
the strip of lead that is used for filling in the case of a butt joint. 



LEAD BURNING 



9 



For lap joints no filling strip is necessary. In the latter case, how- 
ever, it is equally important to scrape clean all surfaces to be welded, 
including both the overlapping edges, otherwise it is not possible 
to do sound work. The illustrations represent the best methods of 
executing the various types of sheet-lead burning. A (Fig. 5) is a butt 




Figs. 5 and 6. — Lead-Burned Joints. 

A, butt joint; B, vertical joint; C, vertical lap joint; D, lapped joint with 
metal added. 



joint. Where added metal is required, the fine of weld should be 
about | inch to f inch wide, and thickened up. This is a very strong 
joint. B is a vertical joint, which is lapped, and no additional 
metal is needed. This vertical welding is not as easy as the butt. 
The metal when molten falls very quickly, and unless the welder 
is sharp the molten metal runs right down instead of in the 



10 MODERN METHODS OF WELDING 

line of the joint. Much practice is necessary for this type of 
welding. C (Fig. 6) is a vertical lap joint, too. The same 
methods have to be adopted as with type B. This weld is not 
so good as type B, nor so neat. D is a lapped joint with added 
metal, the weld being about § inch to f inch wide. This is welded 
horizontally. 

In chemical works very often the sheet lead used is 20 to 30 
pounds, and when vertical jointing has to be done with this thick- 
ness it is usual to employ what is known as a moulding tool, which 
is held over the lap. The lead is melted and allowed to fall into this 
moulding tool. As soon as it is cooled, it is pushed up a bit farther, 
melted, and filled again, the operation being repeated until the joint 
line is finished. This moulding tool is simply a forged tool shaped 
half-round on the inside, where it fits against the lead joint; the 
size is about 1 inch by |- inch semicircular, about | inch thick, with 
a handle at the other end. Below is an illustration of one. 




Fig. 7. — Moulding Tool for Heavy Vertical Welding. 

Lead burning, so called, is the autogenous welding of lead with 
a gas torch. The edges of the lead parts are fused together, using 
no solder or other metal except pure lead to fill the joint. The term 
" lead burning " is really a misnomer, as metal is not burnt, but 
simply fused and flowed together. This process only is employed 
for applying lead linings of acid tanks used in chemical plants, 
fertiliser factories, rubber reclaiming works, electroplating shops, 
nitroglycerine huts, and other industries. The widespread use of 
storage-battery starting systems on motor-cars has created a demand 
in garages and battery stations for lead-welding equipment for the 
welding of lead connectors and terminals. 

Lead welding is used to some extent in making up pipe con- 
nections; but tank and storage work are the chief applications for 
which lead-burning equipments are purchased. Considerable skill 
is required of a lead burner to weld lead sheets together without 
burning holes through or causing the lead to drop. But the trade 
is one quickly learned by an intelligent workman. Success depends 
on clean, thorough preparation, suitable equipment, right material 
and right working conditions, as well as personal skill. Two forms 
of joints are used, the butt and the single-lap seams. The latter are 



LEAD BURNING 11 

used almost exclusively in tank burning. Butt joints are used 
mostly in lead-pipe jointing. 

When making a butt joint, the edges of the sheets or pipes should 
be trimmed straight. They may be rasped to 75 to 80 degrees in 
opposite ways, so that when the two sheets are laid together, a 
V groove of 30 degrees or slightly less angle is formed. If a filler 
is to be used, the groove is filled with molten lead, flush or slightly 
above the surface of the sheets or pipes. A preparation of the butt 
joint by bevelling is practised for sheet burning except on very heavy 
lead — so thick, that is to say, that it is rarely used. All thicknesses 
up to, say, 20 pounds to the square foot are butted with square edges 
and generally burned together without using the filler rod. The 
use of the latter slows down the work, on account of the necessitj^ 
of frequently cleaning off the oxide film on the rod. A joint made 
without the filler rod is slightly thinner than the sheet; but this is 
rarely objectionable. When burning a butt joint with the filler 
rod, the flame is played on the sheets until the metal is softened 
to fusing-point, but is still too stiff to flow freely. The added metal 
is supplied from the lead filler rod to fill the V, if prepared for a 
groove. The filling rod is held in the left hand close to the joint, 
so that the heat of the flame melts it and deposits molten lead into 
the joint, alternately heating the sheets and the filler rod to the 
fusing-point, letting a drop fall into place, then whipping the torch 
off momentarily to allow the fused metal to cool. This practice 
is slow and seldom necessary. 

It should be borne in mind that tank linings are made of chemical 
lead — that is, new lead, free from impurities. Ordinary sheet lead 
used for gutters and other purposes is often made of old lead, and 
should not be used for acid tank linings which must be autogenously 
welded. Lap seams are always used in tank linings where a smooth 
surface is not absolutely required. In making a lap seam the top 
sheet should lap over the under sheet about \ inch to f inch. All 
dirt and oxide should be removed carefully from the joint with a 
sharp scraper. Some lead burners prepare for welding by painting 
a strip of asphaltum along the edge about 1 inch wide, letting it 
dry, and then scraping it off about \ inch width next to the edge with 
a sharp scraper, which removes the oxide and the asphaltum. The 
asphaltum tends to hold from breaking down when overheated, and 
thus favours the use of a large flame burning at a fast rate. The 
flame is directed against the top sheet about \ inch from the edge. 
Some burners give the torch a circular motion, the diameter of the 
circular path being from \ inch to | inch ; but the most rapid work 



12 MODERN METHODS OF WELDING 

on level seams is done with no movement except forward. The 
top sheet fuses and unites with the metal beneath, the edge breaks 
down, and the corner is filled with molten lead, which adheres to 
the lower sheet, making a weld about § inch wide. The burner 
dispenses with the use of the lead filler rod or solder stick on lap 
seams, simply melting down the edge of the overlapping sheet, 
causing it to unite with the one beneath. 

In vertical lap seams the torch is generally given an in-and-out 
motion, thus taking the flame close to the lead and then away. 
When the flame is close to the lead a small section of the upper sheet 
over the seam melts, and slides down about \ inch, where it cools 
and unites. The repetition of the torch movement causes this 
action to be repeated, drops of molten lead sliding down the joint, 
uniting each time the torch is held close. This method is used only 
on vertical work, where it is not feasible to do straightaway burn- 
ing. Some welders give the circular motion instead of the in-and-out, 
but the result is practically the same. 

The temperature needed for lead burning is low in comparison 
with that required for welding cast iron or steel, being only 62° F. 
A special torch is employed, which is held in the hand and manipu- 
lated somewhat the same as a soldering iron. These torches may 
be used with acetylene successfully. 

The lead burner necessarily becomes an expert at working lead 
within narrow temperature ranges. He must heat the metal at the 
joint to the fusing-point, but not so much that it becomes liquid 
and drops away. When butt welding with the solder stick, he must 
avoid heating and adding metal so hot that when it drops into the 
joint it burns a hole through instead of filling the groove. He should 
make provision for growth or expansion of the finings of the hot 
tanks. Repeated heating and cooling cause the lead to expand. 
After a period of use the lining will be found in a corrugated condi- 
tion, due to permanent expansion. 

Lead burning of storage-battery connections is comparatively 
easy, and is quickly mastered by anyone having some mechanical 
skill. Handy men soon become sufficiently expert in this class of 
work to burn storage-battery terminals successfully. The danger 
to be avoided is overheating. The operator must learn to clean 
thoroughly the parts to be united, and to apply the flame no longer 
than is required to fuse the metal and bring about union. When 
the connections have been flowed together, the excess metal should 
be wiped off with a woollen cloth greased with mutton-fat or beef- 
tallow. 



CHAPTER III 

MANUFACTURE OF OXYGEN 

Oxygen is invariably the principal ingredient or combustion agent 
used in the cutting of iron and steel in autogenous welding with the 
blowpipe. It is necessary that those handling the blowpipe be 
familiar with its properties, manufacture, storage, and methods of 
use. Oxygen is the most widely distributed of all bodies. It 
exists in a state of mixture in the air, which contains one-fifth of its 
volume of this gas. Water is a compound of oxygen and hydrogen. 
It is a colourless, tasteless, and odourless gas. One litre of oxygen 
at 0° C. and atmospheric pressure weighs 1 43 grammes, its density 
is 1-1056, its chemical symbol 0, its atomic weight 16. The 
characteristic property of oxygen is its power of supporting com- 
bustion ; a glowing candle will instantly burst into name if plunged 
in a jar of oxygen. 

Iron heated to redness burns readily in air or oxygen. This 
unique phenomena is the whole secret of the cutting of iron and steel 
with a jet of oxygen (which will be described under " Cutting Iron 
and Steel " in a later chapter). The combustion is a chemical 
reaction between the oxygen and the body which burns with it. 
The product of the combustion is called " oxide." 

The manufacture of oxygen can be carried out by several pro- 
cesses, some of which are the barium oxide, the electrolysis of water, 
and the Linde process of the fractional distillation of liquid air, 
which brings about the production of pure oxygen. In 1886, on 
the present site of the British Oxygen Companj^'s works in West- 
minster, a large oxygen plant was erected, which must take a lead- 
ing position in any article dealing with industrial gases. The plant 
was installed by Brin's (now the British) Oxygen Company. 
Although in itself a qualified success, it led to the development by 
that Company of a process which was destined to supersede all other 
known methods of manufacturing oxygen, and greatly to enhance 
the commercial value of the gas. 

The Brin process of producing oxygen is based on the barium- 
oxide process, first suggested by the eminent chemist Boussingault 
in 1857. Boussingault discovered that at a temperature of about 

13 



14 MODERN METHODS OF WELDING 

1,000° F. the monoxide of the metal barium would absorb oxygen 
readily from the atmosphere, with the resulting formation of the 
dioxide, and that at a higher temperature of about 1,600° E. the 
oxygen thus absorbed would be given off again, and monoxide 
restored to its original condition, ready for the cycle to be repeated. 
Continuous efforts were made to establish a commercial process for 
the production of oxygen on this apparently indestructible reaction 
of barium oxide. In spite, however, of its chemical simplicity, 
many practical difficulties arose, which remained unsurmounted 
until the event of the Brin's Oxygen Company in 1886. The Com- 
pany was formed to work the patents of the two French chemists 
whose names it bore. Initial experiments, conducted on a small 
scale under these patents, had met with considerable success, so that 
a large plant was laid. 

It will, however, be seen from what has already been stated that 
the Company's old title was always somewhat of a misnomer. The 
process which has made them not only the oldest and leading gas 
compressors of the day, but also the pioneers of the gas cylinder in- 
dustry, has always been more British than Brin. Although now only 
of historical interest, the barium process is entitled to more than a 
passing recognition in any description of the development of industrial 
oxygen, because the industry was not only founded, but was success- 
fully conducted by means of that process for more than twenty years, 
during the whole of which time, although many other methods of 
producing oxygen were proposed and tried in this country and 
abroad, the barium process remained in sole possession of the field. 
Furthermore, it is worthy of note, in these days when it is customary 
to credit any country but our own with industrial enterprise, that 
in Germany, France, and the United States, the oxygen industry 
was started with the barium, designed and erected by the British 
Oxygen Company, who have acquired the British patents of Pro- 
fessor Linde and Dr. Hampson. These two inventors are the authors 
of the self -intensive system of liquefying air, on which are based the 
numerous processes introduced in recent years, with extravagant 
and preposterous claims that have gone far to bring liquid air 
into disrepute. A serious scientist saw long ago the only really 
valuable commercial application of oxygen and nitrogen. For 
many years he devoted himself to adopting his system of liquefying 
air for this purpose. That his labours have been crowned with 
success has been proved by the fact that on the Continent the com- 
pany which controls his patents has already erected a large number 
of plants, which are in daily operation, giving most satisfactory 



MANUFACTURE OF OXYGEN 15 

results. It is the Linde plant that the British Oxygen Company 
erected at Westminster and many other great centres. 

Briefly expressed, the process consists of liquefying the air com- 
pletely in the first instance by the self-intensive system. Whilst 
obtaining almost complete transference of heat from the compressed 
air entering the apparatus to the liquefied air, the liquid is submitted 
to a special process of rectification, by means of which oxygen of 
any degree of purity up to 98 or 99 per cent, can be obtained. The 
plant is driven by a Diesel engine, which develops som 35 h.p. 
Air is compressed by three stage compressors, belt-driven. Between 
each stage of compression the air is restored to normal temperature 
by passing through coils contained in a cooler, through which water 
circulates. The system of purification of the air is very complete, 
all the moisture and carbolic acid being practically eliminated, 
first in the purifiers containing unslaked lime and calcium chloride, 
while the final traces of moisture are subsequently removed by 
freezing in a forecooler, which is employed, partly for this purpose, 
partly to precool the air before it enters the separators. The lower 
part of the forecooler is reduced in temperature by a small C0 2 
refrigerating machine of the usual type made by the Linde British 
Refrigerating Company, but the upper part is cooled by the waste 
nitrogen from the separator. 

The interchange is so effective that, before the nitrogen is 
returned to the atmosphere, it has taken so much, heat from the in- 
coming compressed air that it leaves the forecooler only a few degrees 
below normal temperature. The compressed air, on the other hand, 
leaves the bottom of the forecooler at a temperature considerably 
below freezing-point, and then enters the top of the separator, passing 
downwards to a series of coils, which are so constructed as to be 
surrounded by both the outgoing cold gases. The bottom of the 
separator contains liquid air, or, more correctly speaking, liquid 
oxygen. The compressed air, on its way to the expansion point, is 
conveyed through the liquid, by which means it is largely con- 
densed. It then passes through the regulating valve, at which 
point it expands, and is ultimately discharged into the top of an 
inner central chamber which forms the rectifying column, in which 
the separation of oxygen and nitrogen is effected, oxygen descend- 
ing in a liquid state to the bottom of the separator, nitrogen ascend- 
ing in a gaseous or vaporous condition to the top. 

The nitrogen is allowed freely to discharge into the atmo- 
sphere through the forecooler, as already explained; the oxygen is 
allowed to boil off in any desired quantity by the adjustment of a 



16 MODERN METHODS OF WELDING 

discharge valve. Both gases, however, on leaving the separator, 
are kept in intimate contact with the cells conv^ing the incoming 
air, so that before leaving the apparatus the heat of the incoming 
air has been mostly transferred to the gases. The plant is very 
conveniently arranged, and consists of two separators and two fore- 
coolers, one of each being worked at a time. In this way continuous 
working is ensured, for when ice (due to entrapped traces of moisture 
in the air) has accumulated to such an extent as to cause a stoppage 
in one separator, the other can be put in operation, whilst the first 
is allowed to thaw. In practice, freezing is found to occur after six 
to seven days of continuous work. 

The description here given represents the normal working of the 
plants. But before pure oxygen can be produced the separator 
has to be cooled down, and a considerable quantity of liquid pro 
duced. This operation takes about three hours, during which time 
the compressed air circulating through the coils is (by the adjustment 
of the regulating valve) maintained at a pressure of about 2,500 
pounds per square inch. Afterwards, when the oxygen is being 
produced, the pressure is about 800 pounds per square inch, at which 
pressure it continues to work. 

Oxygen obtained from liquid air may contain more or less nitro- 
gen. That obtained by the electrolysis of water might contain a 
little hydrogen. These two gases are considered as impurities. 
If hydrogen were present to an appreciable extent, it would have the 
disadvantage of forming with the oxygen an' explosive mixture. 
It has been demonstrated that in the cutting of iron and steel by the 
blowpipe cutters, the presence of nitrogen, even in small quantities, 
has an adverse effect on the quality and rapidity. Oxygen com- 
pressed in cylinders is generally delivered containing 96 to 99 per 
cent, of oxygen; but the commercial guarantee may be as low as 
95 per cent. The British Oxygen Company guarantee the quality 
of their oxygen as 98-5 to 99 per cent., and many experiments carried 
out by the author confirm this. 

Analysis is conducted by acting on a definite volume of gas 
with a chemical which rapidly absorbs the oxygen and leaves the 
impurities intact (hydrogen, nitrogen, or carbon dioxide). The 
quantity of gas absorbed, compared with the original volume, gives 
the degrees of purity. The analysis is generally done in graduated 
test-tubes, as a rule of 100 centimetres capacity and graduated 
to 100. The absorbent liquid takes the place of the oxygen ab- 
sorbed, so that when the reaction is over it is only necessary to read 
off the level of the liquid to know the purity of the oxygen. 



CHAPTER IV 
MANUFACTURE OF HYDROGEN 

These two gases — -oxygen and hydrogen — are now manufactured 
on very large scales. Hydrogen can be very much more freely 
obtained than in the past, and will be more used in future for weld- 
ing purposes. There are very few who are acquainted with oxy- 
hydrogen as applied to welding at the present time, although it was 
in extensive use until the advent of calcium carbide in large com- 
mercial quantities, which generate the acetylene gas. The latter 
was employed, in combination with oxygen, for use in the blow- 
pipe for welding, giving a very much higher temperature of 6,000° F. 
against the oxy-hydrogen flame's 4,000° F. 

There are many advantages in using oxy-hydrogen blowpipes. 
Firstly, the hydrogen is supplied in cylinders, the same as oxygen. 
Therefore it can practically be used anywhere. There is no wasted 
gas, no expense in initial outlay for generators or fixing of piping, 
no messy substance to clear away, as in acetylene generators, the 
two gases, oxygen and hydrogen, under equal pressures, thus ensur- 
ing a constant, steady flame. This blowpipe is also well adapted for 
the burning of lead and the welding of aluminium, because the heat 
of temperature is not so high, but is suitable for these metals. How- 
ever, there is the disadvantage of not being able to get high enough 
temperature to weld heavy mild steel or cast iron, as the heat is 
absorbed and there is loss by conductivity. It is practically im- 
possible to weld steel plates exceeding T V inch thick. 

The flame is produced by the mixing of two volumes of hydrogen 
and one of oxygen. This is the theoretical mixture; but the author 
found in practice that it required, to maintain a good heat to com- 
plete a proper weld, three parts of hydrogen to one of oxygen. 
Hydrogen and oxygen have strong affinity for each other. Their 
combination occurs with great explosive violence, the product being 
water in the form of steam. This steam is, of course, superheated 
in the hot flame, which process of dissociation involves a consumption 
of heat, which is abstracted from the flame, hence an oxidising effect 
on the weld. This can only be avoided by feeding the flame with 

17 2 



18 MODERN METHODS OF WELDING 

an excess of hydrogen (in practice four to five volumes of hydrogen 
to one of oxygen), whilst, on the other hand, only that amount of 
heat can be obtained which is disengaged in the combination of the 
two volumes of hydrogen and one of oxygen. The large excess of 
hydrogen required to prevent oxidation furnishes in itself one way 
why welding by means of the hydrogen-oxygen flame is frequently 
uneconomical. A further reason, however, lies in the fact that the 
temperature of the flame, in consequence of this excess of hydrogen, 
is essentially lower than it ought to be. In spite of this, it is found 
in practice that for thin plate welding the oxy-hydrogen blowpipe 
has certain advantages. The flame is more diffused than in the case 
of oxy-acetylene flame, hence less liable to melt through and pierce 
the metal. 

Every student, if he is to become a welder, must have a fair 
knowledge of all the materials used and their constituents, as also 
of the gases such as oxygen, hydrogen, and acetylene. Since these 
gases are usually provided in convenient cylinders for commercial 
purposes, the users as a rule are not acquainted with their manu- 
facture or with the source of supply. But it is really essential that 
the users of these gases should be acquainted with the process of 
manufacturing them. It is probable that the war, which has brought 
home to many engineers and business men how easily hydrogen and 
oxygen can be generated, will lead to an increased demand for. these 
gases and to their wider appreciation in industrial processes. 

Where both the decomposition products of water, hydrogen, 
and oxygen can be utilised, electrolytic generation offers advantages 
over the isolation of hydrogen from water-gas, which is a cheaper 
method when worked on a really large scale. In the laboratory 
the electrolysis of water is a very simple matter. The electrodes 
are placed in acidulated water in a glass cell. Each electrode is 
surrounded by a hood (an inverted test-tube, e.g., in which the gas 
evolved collects). Currents of about two volts give one volume of 
oxygen and two of hydrogen. 

The technical electrolyser is not quite so simple as the laboratory 
cell. The design and construction of automatic apparatus which 
will continuously yield both gases in a pure condition of 90 per cent, 
and more, practically without requiring any attendance, have left 
sufficient scope for the ingenuity of inventors. Glass cells being 
out of the question, the container has to be adapted to the electro- 
lyte. Water itself is a poor conductor to serve as an electrolyte. 
Either sulphur acid or caustic, both of about 20 per cent, concen- 
tration, are used; but the chemicals are merely to increase the con- 



MANUFACTURE OF HYDROGEN 19 

ductivity of the water, which is the electrolyte, and has to be re- 
plenished by feeding distilled water into the cells. The impurities 
of ordinary water, notably chlorine, would tend to corrode the 
apparatus. 

The acid is placed in lead containers, the alkali in iron cells. 
The reversible decomposition of the water itself would only require 
1 -23 volts ; but the potential applied has to overcome the resistance 
of the leads and of the electrolyte, and further the polarisation of 
the electrodes by the gases liberated. Sulphuric acid is a better 
conductor than alkali, but the supertension of the lead cathode is 
decidedly higher. Hence, on the whole, the caustic alkali requires 
a lower decomposition potential. As regards gas purity and, to a 
certain extent, the efficiency, there is not much to choose between 
the acid and the alkali processes, though the number of kilowatt 
hours required for the liberation of 35 cubic feet of the two gases 
varies from 6 down to about 3-5, at volts ranging from 3-6 down 
to 2-3. But in all these figures the decimals become important, 
and there are features justifying a careful selection of a type of 
electrolyser. 

The general preference is for alkali cells. In the Schoop acid 
electrolysers, the two groups of electrodes, anodes, and twice as 
many cathodes, are all lead tubes, open below to let the acid act 
on the lead wires in the tube. Each tube is insulated by a refractory 
hood. The groups are coupled in parallel. 

In the Garute alkali electrolyser, vertical diaphragms of iron 
separate the iron tank into anode and cathode compartments, 
the two groups of iron, electrodes being again in parallel. 

The Schukert electrolyser uses insulating diaphragms and places 
iron hoods in the different compartments to collect the gases. 

The Schmidt cell of the Oerlikon Company is of the filter-press 
type, and the corrugated iron electrodes are coupled in series. They 
are, in fact, bipolar, as in some electrolytic copper baths and in 
bleach cells. 

The electrolysers of the Integral Oxygen Company, London, 
illustrated on p. 20, differ from types mentioned above in so far 
as each cell is self-contained, in having two electrode units, and, 
further, as to arrangements made for the regulation of the gas 
pressure. This is an Integral unit generator. The cells are of the 
Hayard-Flamand type. The early patents of this cell date back to 
1900, but the particulars, the feed and pressure regulation, are later 
inventions. The battery photograph seems to suggest a filter-press 
arrangement, but each cell is independent, and the common features 



20 



MODERN METHODS OF WELDING 



are the water and the gas pipes and the grouping in series. Each 
cell is independent, each has its own feed and discharge devices, 
each consists of a thin, rectangular frame of cast iron, to which two 
cast-iron plates, the electrodes, are bolted, mica insulators being 
interposed. 

The asbestos diaphragm divides the sj>ace of the flat cell vertically 
into two halves, an anode compartment and a cathode compartment. 
Each compartment communicates through Wo ports with a gas 
chamber. The right is the water chamber. Several jars and pipes 




Fig. 8. — 4, 000 -Unit Geneeatoes eoe Pboducing Oxygen and Hydeogen. 



will be seen on the top of the gas chamber. The gas leaves through 
the two outer glass jars — the hydrogen through the jar on the right, 
the oxygen through that on the left — and enters the two gas pipes 
which are in, but not on, the sketch. A third pipe is the distilled- 
water pipe. This is connected with the central jar through which 
the cell is originally charged with caustic soda of 20 per cent. The cell 
discharges a spray of gas and caustic soda ; this frothy liquid spreads 
upon the base plate, which has a raised edge, this ridge preventing 
the liquid from running back into the port and choking it. It 
spreads over to the port and there flows back into the cell. Thus 
a kind of circulation is set up ; the gas itself is further deprived of its 



MANUFACTURE OF HYDROGEN 21 

moisture by having to force its way through a gas tap in the glass jar, 
which contains an inverted bell of iron. The liquid is intercepted 
between this bell and the jar, the top of which is joined to the gas 
pipe. The cells are worked at a temperature of about 55° C. The 
guaranteed purity of the gases evolved is oxygen 99 per cent., 
hydrogen 99-5 per cent. During recent trials at Farnborough the 
oxygen purity was maintained at 99-8 per cent., which was an 
exceptionally high figure. 

It must be noted that the gases are not purified in any way, but 
enter the gas holders or cylinders as they leave the glass jars. The 
average potential is about 2-2 or 2-3 volts per cell, at the normal 
current of about 600 amperes. Each cell has a rated output of 
4-8 cubic feet of oxygen and 9-6 of hydrogen, and gives an average 
yield of 4 cubic feet of oxygen, and twice as much hydrogen. 



CHAPTER V 
MANUFACTURE OF CARBIDE 

The manufacture of calcium carbide is carried out on such exten- 
sive lines that any student of welding should make himself conver- 
sant with its manufacture. Acetylene was discovered by Davy 
in the chemical laboratory in the year 1836. Many methods of 
preparing the gas were described by various experimenters, the 
majority of which are only of academic interest. But it may be 
mentioned that in 1840 Hare, by heating in an electric arc a black 
residue obtained by heating a mixture of mercuric cyanide and 
lime, arrived at a compound which was undoubtedly calcium car- 
bide, although not recognised as such at the time. 

The next date of importance is the year 1862, in which the German 
chemist Woehler (whose name is well known amongst chemists as 
the discoverer of synthetic urea and other important bodies, includ- 
ing aluminium) obtained " calcium of carbide " decomposed water 
with formation of calcium hydrate and acetylene. It is hard, 
really, to say who was the actual discoverer of calcium carbide. 
It was Moisson, " the king of experimental savants," who published 
his classic investigations. His results were obtained as factors in a 
magnificent research, every step in which was logically worked out 
and verified; a research which will ever stand out as a scientific 
classic. But the fact remains that he only attained and published the 
discovery of the direct formation of calcium carbide in the electric 
furnace to find that his work had been forestalled by a few months 
by the chance observation of an engineer who, although devoid of 
chemical knowledge, yet had sufficient acumen to grasp the commer- 
cial importance of the discovery. Anyone who, with a mind free 
from prejudice, reads the evidence on this subject, is forced to the 
conclusion that the world owes " commercial acetylene " to the 
Canadian engineer, Willson, and the shrewd business men who 
supported him. 

Moisson obtained crystallised calcium carbide during a systema- 
tic and masterly research upon the products of the electric furnace. 
His first paper described an electric furnace, which he distinctly 
stated was not an industrial apparatus, but for research purposes 

22 



MANUFACTURE OF CARBIDE 23 

only. His work consisted in the preparation of crystallised metallic 
oxides such as those of calcium, strontium, barium, magnesium, 
aluminium, iron, chromium, etc. He then dealt with fusion and 
volatilisation of some refractory bodies and metals. This was 
followed by his classical research on the different varieties of carbon 
and the formation of the diamond. The description of the forma- 
tion of calcium carbide is included in a study of the carbides, 
silicides, and the borides. After a brief review dealing with the 
work of Berthelot, Woehler, and Travers, who in 1893 obtained a 
mixture containing some carbide, Moisson writes : 

" The question had reached this point when, in a note appearing 
in the Comptes Rendus cle P Academie des Sciences on December 12, 
1892, I made public for the first time the formation in the electric 
furnace of a carbide of calcium fusible at a high temperature. 
This is what I wrote on the subject. If the temperature reaches 
3,000° C, even the furnace material, the quicklime, melts and flows 
like water. At this temperature the carbon quickly reduces the 
oxide of calcium (lime), the metal itself is liberated in abundance; 
it unites readily with the carbon of the electrodes to form a carbide 
of calcium, liquid at a red heat, which is easy to recover. Follow- 
ing this research, I presented to the Academie des Sciences a note 
of carbide of calcium on March 5, 1894, another note of carbides 
of barium and strontium on March 9, 1894. In this work I showed 
that in a high temperature of the electric furnace there exists only 
one compound of carbon and calcium. This compound was crystal- 
line; I established its formula by analysis, and in the study of its 
properties I made it clear that the bodies decompose in water, 
liberating the gas acetylene absolutely pure." 

This was the starting-point of the acetylene industry. 

At the end of a patent, No. 492,377, U.S.A., on the preparation 
of aluminium bronze, M. Thos. Willson made an allusion to an inter- 
minate carbide of calcium as well as to a great number of other 
bodies, elements or compounds, but did not give an analysis of the 
two compounds obtained, nor even mentioned that this product 
decomposes cold water with liberation of any gas whatever. He 
also avoided, with the greatest care, that " bath of fusion " brought 
metallic calcium. 

Moisson prepared his carbide by making an intimate mixture of 
120 grammes of lime from marble, and 70 grammes of carbonised 
sugar, heating for fifteen minutes in a crucible in the electric furnace 
with a current of 350 amperes and 70 volts. He used a slight excess 
of lime to counteract the carbon obtained from the crucible. He 



24 MODERN METHODS OF WELDING 

noted that if any impure lime was used, containing sulphates, phos- 
phates, or silica, these impurities would be found in the acetylene 
liberated from the carbide. Moisson carried out a number of experi- 
ments with impure materials and analysed the gas obtained; also 
studied the physical qualities of the carbide, the gas yield as well 
as its chemical properties and that of acetylene. It is interesting 
to note that he states that " pure and dry " nitrogen does not react 
with carbide even at 1,200° C. Had he continued this experiment 
to a higher temperature he would have probably been the discoverer 
of cyanamide. 

Whatever the facts of the case may be, Moisson's systematic 
and scientific research work and the practical results obtained 
place his name for ever in an unassailable position in the history of 
the industry. From the time when Moisson and Willson published 
their investigations, the accepted equation for the production of 
calcium of carbide in the electric furnace from carbonaceous matter 
and lime has always been — 

CaO+3C = CaC 2 +CO. 

This final result may be approximately the production of two 
compounds, CaC 2 and CO; but the reaction, or rather, reactions 
which take place before the final stage is reached certainly appear 
to be far more complex. The conversion of the raw material into 
carbide appears to take place in steps. 

In the past, every person who had cheap water-power available 
believed that he had the Alpha and Omega for making cheap carbide, 
even if there was no limestone or carbon within hundreds of miles. 
To equip a modern factory, a very large capital is required, and a 
suitable site, where cheap water-power is available, near to lime- 
stone, coal, and coke. The power for electric energy, in the case of 
every carbide factory in existence, is supplied from a hydro-electric 
station, where the prime mover, or force, is falling water — in other 
words, a waterfall. This falling water passes through turbines or 
Pelton wheels. The type of turbine is decided by the head or volume 
of water available. These turbines drive dynamos or electric 
generators ; some of these generators are used in the electric furnaces 
for the melting of the carbon and the lime for producing the carbide 
of calcium. 

An electric carbide furnace as a rule consists simply of a steel case 
or box, or a steel-framed case or box lined inside with suitable 
refractory material, having a tapping hole very similar to a tapping 
hole in an iron-furnace or cupola. In some of the furnaces electrodes 
are fixed in the bottom of the furnace; in others the electrodes are 



MANUFACTURE OF CARBIDE 25 

suspended from the top. Each of the electrodes is held in various 
kinds of holders, which are connected to busbars. The electrodes 
are made of carbon. The materials used in the manufacture of 
carbide of calcium are primarily — ■ 

(a) Carbon for the charge in the form of coal or coke, 

(b) Carbon for the electrodes, 

(c) Lime. 

Coal. — Only one form of coal, anthracite, has up to the present 
given anything like satisfactory results. An anthracite coal con- 
taining not more than 4 per cent, of ash and not more than 0-040 
per cent, of phosphorus will serve admirably in a modern furnace. 

Limestone. — Mountain limestone is the stone composing the 
limestone ranges known to most of us. The best stone is found in 
the Buxton and Settle Hills districts. There is also oolitic limestone 
(so called because of the resemblance to a mass of fish roe), made up 
of small rounded grains of carbonate of lime. Chalk is fine-grained 
limestone, consisting of finely commuted shells. Magnesia lime- 
stone is a limestone mixed with more or less magnesia. This is 
very suitable for carbide-making. The principal impurities present 
in limestone used for carbide-making are magnesia, alumina, silica, 
iron oxide, sulphur, and alkalies. The maximum quantities of 
impurities permissible in good limestone for carbide should be 
about 0-50 per cent, of magnesia (MgO), 0-50 per cent, of alumina 
and iron oxide, 0-01 per cent, of phosphoric acid (P 2 5 ), about 1 to 
1-2 per cent, of silica (Si0 2 ), and only traces of sulphur. This 
corresponds to a stone containing about 97 to 98 per cent, of 
carbonate of lime. 

Carbide, as now made by a first-class factory, yields 310 litres 
per kilogramme (4-95 feet per pound), and contains, therefore, 
89 per cent, of pure carbide, 11 per cent, of impurities. A metric 
ton of commercial carbide will contain 890 kilogrammes of pure 
carbide. To produce this 890 kilogrammes of pure carbide in a 
metric ton, based on the lime of 96 per cent, purity, coke with 6 per 
cent, of ash, the following will be theoretically the quantities of raw 
materials for a metric ton of carbide — 

56 890 
Lime 7T7 x 77-777, =811 kilogrammes. 
64 0-96 ° 

ni 36 890_. 
Coke 64 0^96 ~ 521 
Total kilogrammes 1,332 =2,797 pounds. 

(1 kilogramme =2-2 pounds.) 



26 MODERN METHODS OF WELDING 

Therefore it takes 1,332 kilogrammes of materials to produce 
890 kilogrammes of commercial casbide. Carbide is produced in 
the electric furnace by the fusion of coal approximate!} 7 30 parts 
by weight, lime 50 parts by weight, to a temperature reaching 
4,000° C. 

Under the enormous temperature of the electric furnace (which 
is carried by the carbon electrodes) the lime and carbon combine. 
The liquid carbide which results is tapped from the furnace (the same 
as the blast furnace or foundry cupola) into receptacles which, 
when cooled, are transported to the crushing machines, which break 
them up. Then on the mechanical graders, which separate the 
various sizes; the carbide is then packed into drums, and the 
covers are hermetically sealed. 

The formula of carbide of calcium is represented by CaC 2 ; it 
is made of 62-5 per cent, of calcium. 

Use 1-4 pints of water to each pound of carbide in water-to- 
carbide generators, 5 pints of water in carbide-to-water generators. 
This should assure full decomposition. Carbide should yield 
4-8 cubic feet of acetylene for every pound of carbide placed in 
the generating chambers. There are various apparatus for testing 
the carbide on the market. When a sample is tested it must be 
broken up in a mortar to about J-inch .mesh, then screened to 
remove the dust as rapidly as possible, then weighed out in a limited 
quantity accurately by a chemist's scale. The carbide is then 
placed in the generating chambers immediately, the water turned 
on (the height of the bell should be marked before the water 
is turned on); then, when the generation has ceased, the bell 
should be marked and then measured with the already provided 
instruments. 



CHAPTER VI 
ACETYLENE 

Acetylene or, as it is scientifically named, "ethine," is a simple 
hydrocarbon consisting of 24 parts by weight of carbon and 
2 parts by weight of hydrogen; its chemical symbol, C 2 H 2 , 
meaning it is a compound of two atoms of carbon combined with two 
atoms of hydrogen. It is a clear, colourless gas, of a specific gravity 
of 0-92. It is, owing to its synthetic formation, the most pure, 
at the same time nearly the richest hydrocarbon gas, containing 
no less than 92-5 per cent, of carbon when perfectly pure and free 
from water vapour. It has an illuminating value of 50 candle- 
power per cubic foot. 

It has a most unmistakable and penetrating odour. When 
present in the proportion of only 1 part in 10,000 parts of air it 
is distinctly perceptible long before there is sufficient gas present 
to cause explosion. Therefore it can be at once detected, and an 
explosion prevented. One burner passing 1 cubic foot per hour 
in a room of 2,500 cubic feet area for a period of nine or ten hours 
would not be sufficient, with the same quantity of air, to make an 
explosive mixture. The largest acetylene burners only pass 1 cubic 
foot per hour, against the 5 cubic feet of coal-gas. It is, therefore, 
obvious that the prevailing popular belief as to acetylene being 
more dangerous than coal-gas is a fallacy. 

Acetylene and oxygen ignite at a temperature of 400° C. The 
temperature of combustion is 4,000° C. Acetylene, although 
practically pure gas, usually contains some impurities in a greater 
or less proportion, mostly sulphuretted and phosphuretted hydrogen 
due to the presence of sulphate of calcium, gypsum, and calcium 
phosphide in the lime, or to the sulphur and phosphorus in the 
coal and coke. Acetylene is always contaminated with ammonia, 
formed by the combination of nitrogen derived from the coke with 
the hydrogen of the water during decomposition of the carbide. 
That acetylene is a poisonous gas has been proved to be untrue. 
When pure it is relatively harmless. The range of explosibilitj' 
is wider in the case of acetylene than of coal-gas. Mixtures having 
less than 5 and more than 60 per cent, are practically non-explosive. 

27 



28 MODERN METHODS OF WELDING 

Acetylene, being an endothermic compound, is liable, when pure, 
if compressed without at the same time being cooled, to explode 
spontaneously. Acetylene is soluble in water and many other 
liquids. It can be liquefied at a pressure of about 325 pounds per 
square inch and forms a mobile and highly refractory liquid, much 
lighter than water. 

The reactions that occur when carbide and water are brought 
into contact belong to the class which chemists usually term double 
decompositions. Calcium carbide is a chemical compound of a metal 
calcium with carbon containing one chemical " part," or atomic 
weight, of the former united to two chemical parts of the latter. 
Its composition is expressed in symbols by CaC 2 . Similarly, water 
is a compound of two chemical parts of hydrogen with one of oxygen, 
its formula being H 2 0. When these two substances are mixed to- 
gether, the carbon of the calcium carbide leaves the calcium unit- 
ing together to form that particular compound of hydrogen and 
carbon, or hydrocarbon, which is known as acetylene, whose formula 
is C 2 H 2 , while the residual calcium and oxygen join together to 
produce calcium oxide of lime (CaO). Put into the usual form of an 
equation, the reaction proceeds thus : 

CaC 2 +H 2 0=C 2 H 2 +CaO. (1) 

This equation not only means that calcium carbide and water 
combine to yield acetylene and lime; it also means that one chemical 
part of carbide reacts with one chemical part of water to produce one 
chemical part of acetylene, one of lime. But these four chemical 
parts, or molecules, which are equal chemically, are not equal in 
weight, although, according to the common law of chemistry, they 
each are a fixed proportion one to the other. Hitherto, for the sake 
of simplicity, the by-product in the preparation of acetylene has been 
described as calcium oxide, or quicklime. It is, however, one of the 
characteristics of this body to be hygroscopic, or greedy of moisture, 
so that if it is brought into the presence of water, either in the form 
of liquid or vapour, it immediately combines therewith to yield 
calcium hydroxide, or slaked lime, whose chemical formula is 
Ca(OH) 2 . Accordingly, in actual practice, when calcium is mixed 
with an excess of water, a secondary reaction takes place over and 
above that indicated by equation (1), the quicklime produced com- 
bining with one chemical part or molecule of water, thus : 

CaO+H 2 = Ca(OH) 2 . 

As these two actions occur simultaneously, it is more usual and 
more in agreement with the phenomena of an acetylene generator 



ACETYLENE 29 

to represent the decomposition of calcium carbide by the combined 
equation : 

CaC 2 +2H 2 0=C 2 H a + Ca(HO) 2 . (2) 

By the aid of calculations analogous to those employed in the 
preceding paragraph, it will be noticed that equation (2) states that 
1 molecule of calcium carbide, or 64 parts by weight, combines 
with 2 molecules of water, or 36 parts by weight, to yield 1 molecule, 
or 26 parts by weight, of acetylene, and 1 molecule, or 74 parts by 
weight, of calcium hydroxide (slaked lime). Here, again, if more 
than 36 parts of water are taken for every 64 parts of calcium carbide, 
the excess of water over these 36 parts is left undecomposed; and 
in the same fashion, if less than 36 parts of water are taken for every 
64 parts of calcium carbide, some of the latter must remain un- 
attacked, whilst, obviously, the amount of acetylene liberated cannot 
exceed that which corresponds with the quantity of substance suffer- 
ing complete decomposition. If, for example, the quantity of water 
present in a generator is more than chemically sufficient to attack 
all the carbide added, however large or small that excess may be, 
no more, and, theoretically speaking, no less, acetylene can ever 
be evolved than 26 parts by weight of gas for every 64 parts by 
weight of calcium carbide consumed. It is, however, not correct to 
invert the proposition, and to say that if the carbide is in excess of 
water added, no more, and, theoretically speaking, no less, acetylene 
can be involved than 26 parts by weight of gas for every 36 parts 
of water consumed, as might be gathered from equation (2) ; because 
equation (1) shows that 26 parts of acetylene may, on occasion, be 
produced by. the decomposition of 18 parts by weight of water. 

From the purely chemical point of view this apparent anomaly 
is explained by the circumstances that of the 36 parts of water 
present on the left-hand side of equation (2) only one-half — i.e., 
18 parts by weight — are actually decomposed into hydrogen and 
oxygen, the other 18 parts remaining unattacked, and merely 
attaching themselves as "water of hydration" to the 56 parts of 
calcium oxide in equation (1) so as to produce 74 parts calcium 
hydroxide appearing on right-hand side of equation (2). When 
the output of gas is measured in terms of the water decomposed, 
in no commercial apparatus, and, indeed, in no generator which can 
be imagined fit for actual employment does that output of gas ever 
approach the quantitative amount, but the volume of the water used, 
if not actually disappearing, is always vastly in excess of the 
requirements of equation (2). On the contrary, when the make of gas 
is measured in the terms of the calcium carbide consumed, a 



30 MODERN METHODS OF WELDING 

percentage may be reached of 80, 90, or even 99 per cent, of what 
is theoretically possible. Inasmuch as calcium carbide is the only 
costly ingredient in the manufacture of acetylene so long as it is not 
wasted — so long, that is to say, as nearly the theoretical yield of 
gas is obtained from it — an acetylene generator is satisfactory or 
efficient in this particular ; and, except for the matter of solubility, 
the quantity of water consumed is of no importance whatever. 

The chemical action between calcium carbide and water is accom- 
panied by a large involution of heat, which, unless due precautions 
are taken to prevent it, raises the temperature of the substances 
employed, and of the apparatus containing them, to a serious and 
often inconvenient extent. This phenomenon is the most important 
of all in connection with acetylene manufacture, for upon a proper 
recognition of it, and upon the character of the precautions taken 
to avoid its numerous evil effects, depend the actual value and 
capacity for smooth working of an acetylene generator. Just as, 
by an immutable law of chemistry, a given weight of calcium carbide 
yields a given weight of acetylene, and by no amount of ingenuity 
can be made to produce either more or less, so, by an immutable law 
of physics, the decomposition of a given weight of calcium carbide 
by water, or the decomposition of a given weight of water by calcium 
carbide, yields a definite quantity of heat — a quantity of heat which 
cannot be reduced or increased by any artifice whatever. 

A very little experiment will show that a notable quantity of heat 
is set free when calcium carbide is brought into contact with water, 
and, by arranging the details of the apparatus in a suitable manner, 
the quantity of heat manifested may be measured with considerable 
accuracy. A lengthy description of the method performing this 
operation is unnecessary. It is sufficient to say that the heat is 
estimated by decomposing a known weight of carbide by means of 
water in a small vessel surrounded on all sides by a carefully jacketed 
receptacle full of water, provided with a sensitive thermometer. 
The quantity of the water contained in the outer vessel being known, 
and its temperature having been noted before the reaction com- 
mences, an observation of the thermometer after the decomposition 
is finished, when the mercury has reached its highest point, gives data 
which show that the reaction between water and a known weight of 
calcium carbide produces sufficient in amount to raise a known weight 
of water through a known therm ometric distance ; and from these 
figures the corresponding number of calories may easily be calculated. 

It is well to remark that there is scarcely any feature in the 
generation of acetylene from calcium carbide and water — certainly 



ACETYLENE 31 

no important feature — which introduces into practice principles 
not already known to chemists and engineers. Once the gas is set 
free, it ranks simply as an inflammable, moisture-laden, somewhat 
impure, illuminating and heat-giving gas, which has to be dried, 
purified, stored, and led to the j)lace of combustion. It is in this 
respect precisely analogous to coal-gas. Even the actual generation 
is only an exothermic, or heat-producing, reaction between a solid 
and a liquid, in which the rise in temperature and pressure must be 
prevented as far as possible. Accordingly, there is no fundamental 
or indispensable portion of an acetylene apparatus which lends itself 
to the protection of the patent laws. 

Treatment of Acetylene after Generation. — The calcium carbide 
manufactured to-day, even the best obtainable, is by no means a 
chemically pure substance. It contains a large number of impurities, 
or foreign bodies, some of which evolve gas on treatment with water. 
To a certain extent, this statement will always remain true in the 
future, for in order to make absolutely pure carbide it would be neces- 
sary for the manufacturer to obtain and employ perfectly pure lime, 
carbon, and electrodes in the electric furnace which did not suffer 
attack during the passage of a powerful current, or he would have to 
devise some process simultaneously or subsequently removing from 
his carbide those impurities which were derived from his impure raw 
material, or from the walls of his furnace. Besides the impurities 
thus inevitably arising from the calcium carbide decomposed, how- 
ever, other impurities may be added to the acetylene by the action 
of a badly designed generator, or one working on a wrong system of 
construction. Therefore it may be said at once that the crude gas 
coming from the generating plant is seldom fit for immediate con- 
sumption. It must invariably be submitted to a rigorous method 
of chemical purification. 

Combining together what may be termed the carbide impurities 
and the generator impurities, in crude acetylene the foreign bodies 
are partly gaseous, partly liquid, partly solid. They may render the 
gas dangerous from the point of view of possible explosion. They 
may be harmful to health if inhaled, injurious to the fittings and 
decorations of rooms, objectional at the blowpipe orifices by deter- 
mining or assisting the formation of the solid growths which dis- 
tort the flame and so reduce its power ; they may give trouble in the 
pipes by condensing from the state of vapour in the bends and dips, 
or by depositing, if they are already solid, in angles, etc., and so 
causing stoppages. 

It will be apparent without argument that a proper system of 



32 MODERN METHODS OF WELDING 

purification is one that is competent to remove the carbide impurities 
from acetylene, as far as removal is desirable or necessary. It should 
not be necessary to extract generator impurities, because the proper 
way to deal with them is to prevent their formation. Vapour of 
water almost always accompanies acetylene from the generator, 
this being due to the fact that in a generator where the carbide is in 
excess the temperature tends to rise until part of the water is vapor- 
ised and carried out of the decomposing chamber before it has an 
opportunity of reacting with the excess of carbide. In large plants 
the extraction of the moisture may take place in two stages. The 
gas from the generator is generally passed slowly through a condenser, 
although in smaller generators it is often quite suitable for the gas 
to pass through the water of the generator in order to remove the 
soluble impurities. The generator impurities present in the crudest 
acetylene consist of hydrogen and nitrogen- — i.e., the main con- 
stituents of air; the various gases — liquid and semisolid bodies — 
which are produced by the polymerising and decomposing action of 
heat upon the carbide, water, and acetylene in the apparatus ; and, 
wherever the carbide is in excess in the generator, some lime in the 
form of very fine dust. This lime dust, which is calcium oxide or 
hydroxide, carried forward by the stream of gas in extremely fine 
subdivision, is liable to be produced whenever water acts rapidly 
upon an excess of calcium carbide. It occasionally appears in the 
alternative form of froth in the pipes leading directly from the 
generating chamber. This froth is hard to break up. 

A purifying system must remove generator impurities, unless the 
generator is so perfect that it does not give them off. With the 
exception of the gases which are permanent at atmospheric pressure 
— hydrogen, carbon monoxide, nitrogen, and oxygen — which, once 
produced, must remain in the acetylene, extraction of these im- 
purities is quite simple. The dust or froth of lime will be removed 
in the washer where the acetylene bubbles through water. The 
dust itself can be extracted by merely filtering the gas through 
cotton-wool, felt, or the like. The least volatile liquid impurities 
can be removed partly in the condenser, partly in the washer, partly 
by a mechanical dry-scrubbing action of the solid purifying materials 
in the chemical purifier. To some extent the more volatile liquid 
bodies may be removed similarly. 

Carbide Impurities. — Neglecting very minute amounts of carbon 
monoxide and hydrogen as being insignificant from the practical 
point of view, the carbide impurities of the gas fall into three mam 
categories : those containing sulphur, those containing silicon, those 



ACETYLENE 33 

containing gaseous ammonia. The phosphorus in the gas becomes 
calcium phosphide in the calcium carbide which is attacked by 
water, and yields phosphuretted hydrogen (or phosphine). The 
calcium phosphide, in its turn, is produced in the electric furnace 
by the action of the coke upon the phosphorus in phosphatic lime. 
The sulphur in the gas comes from aluminium sulphide in the carbide. 
Even in the absence of aluminium compounds, sulphuretted hydro- 
gen may be found in the gas of an acetylene generator. In the gas 
itself the ammonia exists as such, the phosphorus mainly as phos- 
phine. The sulphur is present partly as sulphuretted hydrogen, 
partly as organic compounds analogous, in all probability, to those 
of phosphorus. Ammonia and sulphuretted hydrogen are both 
soluble in water, the latter more particularly in limewater of an 
active acetylene generator, while all other bodies referred to are 
completely insoluble. Therefore a proper washing of crude gas 
in the water should suffice to remove all ammonia and sulphuretted 
hydrogen from the acetylene. 

When acetylene was first introduced on commercial lines, 
the generator manufacturers began to attack the problem of 
purification in a perfectly empirical way, either employing some 
purely mechanical scrubber, filled with moist or dry porous material, 
or perhaps coke or the like, wetted with dilute acid. At first sight 
it might appear that the methods of treating coal-gas would suit 
acetylene, as the latter contains two of the impurities, sulphuretted 
hydrogen and ammonia. Setting on one side, as worthy of atten- 
tion, certain compositions offered as acetylene-purifying materials, 
whose constitutions have not been developed, and whose action 
has not been certified by respectable authority, there are now three 
principal chemical reagents in regular use. These are chromic acid, 
cuprous chloride, and bleaching powder. Chromic acid is employed 
in the form of solution acidified with acetic acid. In order to obtain 
the advantages attendant upon the use of a solid purifying material, 
this is absorbed in that highly porous and inert silica known as 
infusorial earth or " kieselguhr." This substance was first recom- 
mended by Ullmann, and is termed commercially " heratol." As 
sold, it contains about 136 grammes of chromic acid per kilogramme. 
Cuprous chloride is used as a solution in strong hydrochloric 
acid, mixed ferric chloride, similarly absorbed in " kieselg hr." 
From the name of its proposer, this composition is called "franko- 
line." It will be observed that both heratol and frankoline are 
powerfully acid, whence it follows that they are capable of extract- 
ing any ammonia that may enter the purifier. But this material 



34 MODERN METHODS OF WELDING 

should be in an earthen vessel. Heratol changes somewhat in colour 
as it becomes spent, its original tint, due to the chromic acid, altering 
to a dirty green, characteristic of the reduced state of the chromium. 

Frankoline has been asserted to be capable of regeneration or 
revivification — i.e., when spent it may be rendered fit for further 
service by being exposed to the air for a time, as is done with gas 
oxide. 

Of all these materials, heratol is the completest purifier of 
acetylene, removing phosphorus and sulphur most rapidly and 
thoroughly, and not appreciably diminishing in speed or efficiency 
until its chromic acid is practically used up. On the other hand, 
heratol does not act on pure acetylene, so that purifiers containing 
it should be small in size, and frequently recharged. 

Frankoline is very efficacious as regards phosphorus, but it does 
not extract sulphur. The purifying materials mentioned may be 
valued by their price, proper allowance being made for the quantity 
of gas purified per unit weight of substance taken. The annexed 
table shows approximately : 

(1) The number of litres of gas purified by 1 kilogramme of 
the substance, and 

(2) The number of cubic feet purified per pound. 





Litres per 


Cubic Feet 




Kilogramme. 


per Pound, 


Heratol 


5,000 


80 


Frankoline 


9,000 


144 


Puratylene 


1,000 


156 



Opinions differ as to the maximum volume of acetylene which a 
certain variety of purifying material will treat. If 1 pound of a 
certain substance will purify 200 cubic feet of normal crude acetylene, 
that weight is sufficient to treat the gas evolved from 40 pounds 
of carbide, but it will only do so provided it is so disposed in the 
purifier that the gas does not pass through it at too high a speed 
that it is capable of complete exhaustion. 

Purifiers charged with heratol are stated, however, to admit of a 
more rapid flow of the gas than is the case with other materials. 
The ordinary allowance is 1 pound of heratol for every cubic foot 
per hour of acetylene passing, with a minimum charge of 7 pounds 
of the material. As the quantity of the material is increased, the 
flow of the gas per hour may be proportionately increased — e.g., 
a purifier charged with 133 pounds of heratol should purify 144 
cubic feet of acetylene per hour. 



CHAPTER VII 
OXYGEN CYLINDERS 

The rapid and extensive developments of the oxy-acetylene process 
in recent times has led, of course, to a corresponding growth in the 
handling and use of oxygen cylinders. If simple and indispensable 
precautions are followed in manipulating the cylinders and utilising 
the gas they contain, no real danger is present; but many welders 
are entirely ignorant of the care required, and the author proposes 
therefore to mention a few principal points in the construction and 
handling of these cylinders. 

The manufacture, transport, and utilisation of cylinders of com- 
pressed gases were investigated by a Government Committee in 
1895, and, although their recommendations have not been converted 
into law, they form the basis for the manufacture of cylinders and 
the regulation of the gas-cylinder trade. The oxygen cylinders 
usually employed in oxy-acetylene welding contain from 100 to 200 
cubic feet of gas under a pressure of 120 atmospheres, or 1, 800 pounds 
per square inch. The cylinders containing 100 cubic feet are most 
used, the approximate dimensions of this size being 7 inches 
diameter and 49 inches over-all length, including valve. The cylinder 
weighs ajDproximately 1 cwt. The majority of the cylinders are 
made of seamless steel, and the method of manufacture is of interest. 
A flat steel slab, about f inch thick, is raised to a red heat, and sub- 
jected to three hot drawing-through processes. The cylinder is 
next annealed, and then pickled in acid to remove the scale. After 
this it is subjected to about six cold drawings, so as to produce the 
right shape, length, and thickness. The bottom of the cylinder is 
hemispherical and the open end is swaged down, after previously 
upsetting the end of the tube so as to form the neck, which, in turn, 
is screwed to receive the cylinder's valve. 

After manufacture, the cylinders are annealed by the manu- 
facturers, and reannealed, valved, and tested by the compressing 
firm. The cylinders are reannealed every third or fourth year, and 
retested every one or two years. They are stamped on the neck, 
so that at any time in their history they can be traced. The most 
important marks are the annealing and test-mark, giving the date 



36 MODERN METHODS OF WELDING 

of the last testing and annealing. A useful mark on the cylinder 
is that of its capacity or internal volume. A foot is sometimes 
shrunk on the base of the cylinder. This enables it to be placed 
in an upright position, and avoids sudden shocks in manipulation. 
Sectional views through typical oxygen cylinders are shown in 
Fig. 9. The cap is shown separately. 

With regard to the testing of cylinders, ordinary tensile, elonga- 
tion, and bending tests can only be carried out on finished cylinders 
by destroying them. It is useful to carry out tests to destruction 
on about 2 per cent, of the cylinders made at one time to any given 
specification. Tests for cylinders which are to be put into use are 
of two kinds : 

(1) The Hydraulic Test. — The cylinder is subjected to an hydraulic 
pressure, usually about double the intended working pressure. 
If a cylinder stands this test, it should be perfectly safe for the work- 
ing pressure. The hydraulic test gives no information as to whether 
the cylinder is annealed or not or whether the steel is ductile. 

(2) The Stretch Test. — It being necessary to examine whether 
the cylinder has permanently stretched during the hydraulic test, 
compressing firms have introduced an easily applied and sensitive 
test called the stretch test. During the hydraulic test the cylinder 
is placed in a vessel, which forms a water-jacket. A pipe and glass 
tube communicate with this jacket. If there is any expansion of the 
cylinder during the hydraulic test water is driven out of the jacket 
and rises in the glass tube. Oxygen cylinders always contain a 
certain amount of water which it is impossible to eliminate, and 
which accumulates during successive fillings, finally occupying 
several cubic inches. It is therefore necessary carefully to drive 
out the water contained in a full cylinder before screwing the pres- 
sure-reducing valve in position. In this manner the life of the 
cylinder is increased, and the difficulties encountered when using 
large quantities of oxygen (as, for example, in cutting) are removed 
or reduced. 

Cylinders of compressed oxygen can be manipulated without any 
very special precautions. For use they are placed, according to 
shape, upright or lying down. Carefully avoid letting them fall. 
Such accidents do not affect cylinders, but may injure the welders, 
and in many cases damage the reducing valve. The cock or valve 
i£ the delicate part of the cylinder. The welder has only, in theory, 
to open and close the valve at the beginning and the end of the 
work. This operation, so simple in itself, requires certain precau- 
tions. Often on the arrival of the cylinder the valve is hard to 



OXYGEN CYLINDERS 37 

open. The operator should make sure of its working before placing 
the reducing valve in position, so that any powdered oxide or other 
dust is blown away. The oxygen on escaping into the air produces 
a violent hissing. The valve should be opened and closed alternately 
two or three times. The slightest escape can be detected by the 
ear. The reducing valve should now be fixed, care being taken 
to see that the screw on the valve is put in square to the thread of 
the cylinder, so as to avoid damaging the thread. Screw down 
tightly with the spanner supplied with the cylinder. Then open 
the tap on the reducing valve where the rubber pipe fits on, and turn 
on gently the gas at the cylinder tap, and test if there is any leakage 
at the cylinder or valve. If there is an escape, which may be shown 
by the pointer on the gauge rising after the valve of the cylinder has 
been closed, try to screw the valve tighter without overdoing it, 
because it will be difficult to reopen after. If the leak still con- 
tinues, remove the reducing valve, and open the cylinder valve 
briskly two or three times. 

No grease, oil, soap, or any fatty matter must be used, as 
oxygen under pressure has an oxidising action on all these articles. 
This causes heat to be produced, which may start combustion, and 
the conflagration may spread to the ebonite parts of the valve and 
destroy them. The oxygen then escapes in large quantities from 
the cylinder, thus tending to produce a brisk combustion by con- 
tact with a lighted body. The results may be serious. In case the 
leak is considerable and it is possible to stop it by ordinary methods, 
the cylinder should be returned to the manufacturers, with a label 
attached, "Valve faulty," so that the manufacturers can proceed 
to repair it before refilling. 

There are cases of freezing of the reducing valve by the solidifica- 
tion of water -vapour. Particular warning must be given against 
melting the ice by heating with the flame of the blowpipe. This 
is a bad practice, and may lead to accidents. The only thing is to 
use warm water. In order to avoid excessive expansion of the gas, 
and the resulting increase in pressure, the cylinders should always 
be kept away from a warm place. Avoid placing them in the sun 
or near fires. After emptying, the cylinders should be immediately 
returned to the company to be refilled. They generally belong to 
the manufacturers, but one can purchase one's own. Oxygen 
cylinders are carried on the railways at class 2 rates by goods 
train, and empties returned at reduced rates. All sent by rail 
must be fitted with covers, as specified by the Railway Clearing 
House. 



38 MODERN METHODS OF WELDING 

Although much literature on oxy-acetylene welding and cutting 
has appeared in recent years, there has not been any of a general 
character in which concise and comprehensive regulations have been 
given to blowpipe operators. 

One frequently comes across cases of trained and efficient welders 
who are incurring daily risks at their work simply because many 
important precautions and regulations are unknown to them. It 
is safe to say far more welding accidents occur through ignorance 
than through wilful neglect of ordinary safeguards. Only a very 
small proportion of operators have had the advantage of training at a 
welding school. No opportunity should be lost of placing regulations 
bearing on their own security before the large number of men and 
women operators now employed throughout the country. I append, 
therefore, the necessary regulations, and I impress on all operators 
to carry them out for the safeguarding of themselves and others. 

Regulations, Precautions, and Safeguards. 

(1) In placing contracts for oxygen supplies, a guarantee from 
the supplier should be obtained, to the effect that oxygen will only 
be delivered in cylinders which have been- made, annealed, tested, 
and filled strictly in accordance with the recommendations of the 
British Government Departmental Committee of 1896. 

The British railways and all the responsible road and water 
carriers require these conditions to be complied with. 

(2) A guarantee should be also obtained to the effect that the 
oxygen supplied will be not less than 98-5 per cent, quality. 

(3) See that all cylinders supplied with oxygen are painted black 
and fitted with right-hand valves ; never attempt to alter the colour 
of the cylinder or the screwed thread of the valve connections. 

(4) See that cylinders are not exposed to excessive heat. 

(5) Oxygen cylinders should not be exposed to temperature 
exceeding 1,000° F. 

(6) Take care not to lay hot welded or cut material on or along- 
side oxygen cylinders ; and great care must be taken never to allow 
the blowpipe flame or the heat from the same to impinge on the 
oxygen cylinder. 

(7) Carefully avoid the use of oil or grease, or lubricant in any 
form, upon the cylinder valves or fittings, and keep same dry and 
free from grit. 

(8) Never use keys of long leverage to close cylinder valve; 
they give under power, which is injurious to the valves, and fre- 



OXYGEN CYLINDERS 



39 



quently results in broken spindles. If the valve leaks when closed 
with ordinary lever key, it is often due to grit. To remove this, 
open the valve slowly, and then close it sharply. 

(9) After disconnecting a cylinder before it is empty, it 
is desirable to test for leakage 
by pouring some water into the 
valve socket. If no bubbles ap- 
pear in the water, it proves that 
the valve is gas-tight. The valve 
gland can be tested in the same 
way at any time that the valve 
is open, and a regulator at- 
tached, by pouring water into 
the recessed part of the gland- 
nut round the spindle. The 
gland-nut must be tightened up 
if necessary to prevent leakage. 

(10) See that all socket and 
nipple ends are in good order and 
free from grit before fixing regu- 
lators or other fittings by screwing 
up the fly-nut " hand tight." 

(11) Never open the cylinder 
valve suddenly when the regulator 
is fixed. The valve should be 
opened by tapping the key gently 
with the hand. 

(12) Store cylinders under 
cover in an outhouse, or in a 
portion of the premises most 
remote from any source of fire 
risk. Avoid as much as possible 
exposing cylinders to conditions 
which promote oxidisation, and 
return empty cylinders to the 
oxygen factory as quickly as 

possible. Cylinders should be returned with a label bearing 
the customer's name, so that they may be identified and credited 
to him in the oxygen factory. 




Fig. 9.- 



-SeCTION OF AN OXYGEN; 

Cylinder. 



CHAPTER VIII 
ACETYLENE GENERATORS 

General Construction. — Acetylene generators may be divided 
into several classes. For the purpose of description three types 
will be taken — namely, water-to-carbide, carbide-to-water, and the 
dipping or contact generators. We will describe each one by itself, 
and state the advantages and disadvantages as they arise. 

Most people, when taking up oxy-acetylene welding, decide to 
purchase a small portable generator. This is a mistake. Such a 
generator is only intended for occasional use. It frequently 
happens, therefore, that the purchaser finds after a few weeks that 
the generator is not large enough, and he has to purchase a larger 
one. It is very much better to have a large one at first. The first 
cost may be higher, but the advantages are many, and the saving in 
gas would pay for the extra cost in a few months. 

Generators should be well designed by competent men who have 
had years of experience, and everything should be carefully thought 
out and well constructed, somewhat on the following lines : 

(1) Generating casing should be made of strong steel sheets, and, 
after manufacture, galvanised. 

(2) The tubes and fittings all galvanised. 

(3) Two or more generating chambers. 

(4) Generator capable of recharging while working. 

(5) Quite automatic. 

(6) Capable of taking any over generation. 

(7) Washer to absorb the ammonia and sulphurous acid. 

(8) Purifier with chemical composition for the removal of phos- 
phorus and other impurities. 

(9) Large outlet and inlet tubes, so as not to throttle the gas. 

(10) No copper should be used on any part of the generator. 
The production of acetylene by the action of water on calcium 

of carbide is, chemically, one of the simplest of reactions. But in 
practice it is not so simple. The two chief difficulties in the pro- 
duction of acetylene are heating and excess production. Water 
consists of hydrogen and oxygen, the dissociation of which takes 

40 



ACETYLENE GENERATORS 41 

place with the absorption of heat. On the other band, the oxygen 
liberated combines with calcium carbide and produces the action 
more heat than is absorbed by the above reaction. The heat liber- 
ated is 226 calories or 900 B.T.U. per pound of carbide — that is to 
say, 1 pound of carbide would raise 1 gallon of water from 0° to 50° C. 
No device or arrangement can alter this amount of heat liberated; 
but the temperature of the mass altered will not go beyond the 
temperature of boiling water. This result is caused in two ways: 
(1) The water vaporises and acts with the carbide, thus supple- 
menting the heat of decomposition; (2) under the influence of heat 
the lime gives up the water, reaction continues, and if there is no 
external cooling the temperature rises. The generation of acetylene 
at a high temperature is detrimental, and causes polymerisation. 
This is one reason why manufacturers often put the generating 
chambers inside the tanks, so as to have the water all round them, 
and also to have the outlet pipes from the generating chambers 
turned down from the top, so that the gas is passed through the 
water cooled and washed. 

Polymerisation, as stated previously, takes place owing to too 
rapid generation, which results in excessive heat to a temperature 
of 130° F. and causes the lime or spent carbide to turn yellow in the 
carbide trays, being in the form of a tarry substance. 

Carbide gives up sulphide on the action of heat; and the water 
decomposes into hydrogen sulphide and organic sulphur compounds, 
which are very detrimental to acetylene. The unpleasant odours of 
sulphur dioxide are given off on the heating of the gas. 

No generator produces the proper proportion of gas consumed. 
The production, therefore, is either in excess or deficient. Produc- 
tion being in advance, the sudden stoppage of consumption cannot 
possibly correspond to the above arrest of the reaction. 

It is important to note that any particular generator-heating and 
after-generation are in direct relation to the delivery. It is there- 
fore impossible to formulate rules on this point without taking into 
account the delivery. The heating should never exceed a tempera- 
ture of 130° C. The generator bell should be large enough to take 
all the after-generation in the case of stoppage. A well-designed 
and constructed generator needs the minimum of attention. It is 
entirely automatic, only gives gas as required, is strong, and will 
last for a number of years. 

The characteristic point in every generator for welding is its 
flexibility. It should adapt itself to fluctuating employment — 
that is, should rise to the maximum and minimum yield without 



42 MODERN METHODS OF WELDING 

delay, without heating, without jerks. This refers to automatic 
generators only. 

Non-automatic generators are usually of large dimensions, in 
which the gas is made in large quantities in advance and stored in a 
gasometer of from 50 to 500 cubic feet. This method is the most 
practical, most sure, and most economical by a long way, but the 
initial cost is high. 




Fig. 10. — 10-Cwt. Carbide-to-Water Generator. 

Fig. 10 is a photograph of a large generating plant, comprising 
generator, condenser, washer, gasometer, and purifier. It is 
worked on the usual principle. 

Figs. 11 and 12 are carbide-to- water type generators, medium- 
pressure type, which makes it possible for the storage of the 
generated gas, with its accompanying advantage of absolute 
volumetric control. The gasometer obviates the variation of gas 



ACETYLENE GENERATORS 



43 



pressure that is inherent in the pressure generator. No regulating 
or reducing device is necessary, as the acetylene is generated at the 
pressure required for use. The possibility of loss of gas through 
leakage in the line and connections is practically eliminated with 
the low-pressure system. The gas bell provides storage for gas and 
effectively guards against the loss due to after-generation inherent 
in other systems. 

Control of the feed 
mechanism is accomplished 
through the rise and fall of 
the gas bell, and with abso- 
lute gas-pressure. The move- 
ment of the gas bell gives 
a dual motor control — first, 
through a brake; second, 
through a position jaw 
clutch. Special provision is 
made for shutting off the 
motor feed when the gas 
bell is in its lowest position. 

Operation of the genera- 
tor is effected by a small 
but efficient weight-driven 
motor, which automatically 
starts and stops to supply 
the amount of gas being 
used. The motor weights 
always lower approximately 
the same distance for each 
pound of carbide used, and 
constitutes a reliable indica- 
tion of the amount of carbide 
remaining in the machine at 
any time. By the use of 

positive forced feed, it is impossible for more than the proper 
quantity of carbide to be fed in the water. In securing cool, 
and hence efficient, generation, it is necessary to have not less 
than 1 gallon of water capacity per pound of carbide charge. It 
is impossible for the temperature of the gas to rise above the 
boiling-point of water, the acetylene"! bubbling through the water, 
free from some of the impurities. By the time the gas is ready 
to leave the surface outlet its temperature does not exceed that 




Fig. 11. — 50 Pounds Carbide Capacity, 

using 1J Pounds Carbide. 

Height, 62 inches; diameter, 24 inches; 

weight, 450 pounds. 



44 



MODERN METHODS OF WELDING 



of the air by more than a few degrees. These conditions permit 
a yield of pure gas. 

A complete and efficient system of interlocking safety devices 
prevents mistakes in operation due to carelessness or forgetfulness 
when charging the generator. The hydraulic back-pressure valve 

is of unique design. With three 
distinct water seals, it prevents 
the possibility of any oxygen 
entering the generator. The 
generator is equipped with an 
agitator that churns the resi- 
duum thoroughly, allowing it 
to flow freely and quickly when 
the residuum is opened for re- 
charging. 

These generators produce 
acetylene at a pressure of less 
than 15 pounds. After the 
hopper has been filled with 
carbide (l|-inch mesh) it is fed 
to water by means of a re- 
volving disc; surrounding this 
disc are little plows, or scrapers, 
that scrape off a certain quan- 
tity of the carbide as the disc 
revolves. The disc is controlled 
by a governor which is actuated 
by the gasometer. When the 
gasometer reaches a predeter- 
mined r eight, the motor is 
stopped by means of a brake. 
When the gas bell recedes, the 
motor is automatically started 
by releasing the brake. The 
gas passes from the generator 
chamber into the gasometer. 
From there it passes through 
the filter, where physical impurities and suspended matter are 
removed, and then through the hydraulic valve, which is a water seal 
for preventing the reverse flow of gas or air. The gas then passes 
into the service line. The filter consists of a cylindrical shell within 
which felt is placed. Perforated plates are placed at the top and 




Fig. 12. — 100 Pounds Carbide Capacity, 
using 1J Pounds Carbide. 

Height, 76 inches; diameter, 30 inches; 
weight, 550 pounds. Known as Davis- 
Bournonville Pressure Generators. 



ACETYLENE GENERATORS 45 

bottom. The gas passes up through the perforations and felt, which 
collects all dirt, lime, or portions of sludge that would otherwise 
enter the service line with the gas. 

The bell tank is divided by the horizontal partition, the lower 
portion of the tank forming the seal chamber. The stand pipe 
projects downward into this chamber, being sealed with water it 
contains. The function of the seal chamber is to prevent an ex- 
cessive pressure from accumulating within the apparatus, and pre- 
cludes the possibility of a backward or reverse pressure entering the 
generator. Should the pressure of the gas from any cause be in- 
creased above the normal pressure, the seal will immediately break. 
The water will overflow from the seal, filling lip, and release the 
pressure. 

If there should be generated, because of defective or broken 
apparatus or other reasons, a larger volume of gas than can readily 
be held by the gas bell, the bell would be forced upward. In order 
to prevent such an occurrence, there is a stand pipe arranged with a 
series of blow-off holes. This stand pipe is connected to the vent 
pipe. Should the stand pipe rise above the level of the water, thus 
producing a free passage for the gas down the stand pipe through 
the safety vent pipe to the outside air, as soon as the gas bell was 
relieved of the excess gas it would lower gradually and the blow-off 
holes would be again under the water and the flow of gas shut off, 
thus permitting the generator to resume its normal working condition. 
The vent valve, the generator filling valve, and the residuum gate 
are so arranged that they can only be operated in sequence. The 
opening of the residuum gate therefore allows the gas within the 
generator to escape to the outside air before any valve or opening 
from the generator can be made into the room. 



CHAPTER IX 
OXYGEN REGULATORS 

Oxygen-reducing valves are manufactured by various firms, and 
are of various forms. Some are very reliable and, with care, will 
last a good number of years. The reducing valves are fixed to the 
oxygen cylinder by means of a union on the valve. The screws on 
the union are standardised, as likewise the screws on the top of the 
cylinder. In the valve of the cylinder there is a faced surface 




Fig. 13. — Oxygen Regulators: 1 Two Gauges, 1 One Gauge, 1 No Gauge. 



(concave) ; on the regulator tip is a convex-faced and ground surface. 
In fixing the regulator tight in the cylinder, the cylinder spanner 
should be used, and care taken to see that it is tight ; before turning 
the oxygen on, open the tap of the blowpipe supply, then gently 
open the valve on the cylinder and see if all is sound. Turn off the 
blowpipe tap. The regulator must not leak at the cylinder; if it 
does, turn off the oxygen again and tighten up the union. Try the 
gas on again. If still leaking, the regulator should be entirely 
removed, and the oxygen turned on two or three times to blow out 
any grit or dust that may have accumulated inside the valve. 

46 



OXYGEN REGULATORS 



47 



Then fix the regulator again, and test. This time you will probably 
be sound. 

It is most important to note that there is great danger in getting 
oil or grease into the union of the reducing valve, because ignition 
may take place and cause an explosion, doing much damage. 

There are three types of regulators ; one is shown in Fig. 13. No. 1 
has no gauge and, naturally, the cost is less owing to its absence. It 
is not absolutely necessary to have this gauge. The regulator works 



^ #>^ 




Fig. 14. 



-Double Cylinder Connector, in which One can be Used while 
the Other Empty One can be Changed. 



quite as well without, but one cannot tell what amount of gas there 
is in the cylinder; it has got to be used till empty. No. 2 is the same 
as No. 1, but has a gauge fitted, which registers the gas in the cylinder. 
No. 3 is for high pressure and is used for cutting purposes. One 
gauge is for the pressure which is regulated by the tee screw. The 
other indicates the amount of gas in the cylinder. All oxygen 
cylinders are painted black, and have a right-hand thread for fitting 
into the cylinders. These regulators are suitable for every class of 
work for which oxygen and other compressed gases are used. They 
automatically deliver gas from the cylinders at any pressure to which 
they are set. This is very important in welding and for the correct 



48 MODERN METHODS OF WELDING 

mixture of the gases. They are substantial in construction, are 
fitted with a gas expansion device which obviates ignition risks at the 
valve seat, and are specially recommended for use for all kinds of 
blowpipe work in connection with oxygen cylinders. The adjust- 
able screwed socket on the side of the regulator No. 1 is graduated 
in pounds per square inch. The regulator can be set by this to 
any desired constant pressure. 

No. 2 regulator has a high-pressure gauge to register the cylinder 
pressure ; but these pressure gauges, permanently attached to regula- 
tors, are a fruitful source of trouble. They soon become inaccurate 
(particularly the small type so frequently employed), and, being 
delicate in construction, are liable to injury in workshop handling. 
The connector illustrated in Fig. 14 is an excellent substitute for the 
pressure gauge. The regulator is in communication with the cylin- 
ders A and B, one of which can be cut off when not in use. Thus, 
if the valve of the cylinder A and the pipe valve a are open, whilst 
the valve of cylinder B and the valve b are closed, oxygen flows 
from cylinder A through the regulator till it empties. The valve 
of cylinder A is then closed and that of cylinder B opened. Oxygen 
will then flow to cylinder B, whilst the empty cylinder A can be 
removed and replaced by a full one. It will readily be seen that 
a continuous supply of oxygen can be maintained by the employ- 
ment of this connector. For prolonged use, regulators with these 
connectors will be found more convenient and more reliable than 
those fitted with pressure gauges. 

The oxygen should be opened as slowly as possible on to the 
regulator, and the regulating screw should be fully open. This 
avoids the heating by quick compression. This is important for the 
safety of the welder, and preserves the regulator in good working 
order, because sudden pressure on the diaphragm of the regulator 
produces derangement and often puts it out of order through the 
diaphragm splitting. Regulation of the pressure should be secured 
by the regulating screw until the pressure is that stamped on the 
blowpipe to be used, and the outlet valve should be full open. 



CHAPTER X 

REGULATIONS 

Regulations, Precautions, and Safeguards for Oxy- Acetylene Weld- 
ing and Cutting. — There lias been much literature on oxy-acetylene 
welding and cutting in the past, but little has been said as to the 
precautions necessary. All students and others interested in the oxy- 
acetylene welding and cutting should study these regulations very 
closely. One frequently comes across cases of trained and efficient 
welders who are incurring daily risks at their work simply because 
many important precautions and regulations are unknown to them. 
It is safe to say that far more welding accidents occur through ignor- 
ance than wilful neglect of ordinary safeguards. 

The general regulations which it is necessary to observe in 
connection with oxygen cylinders have been given above. I now 
add similar regulations with regard to carbide and to acetylene 
generators. 

Carbide. 

(1) Carbide must be stored in iron or steel vessels, hermetically 
sealed. 

(2) The vessels should be kept in a dry and well-ventilated place. 

(3) No artificial light capable of igniting inflammable vapour 
should be employed near these vessels nor in any room where carbide 
is stored. 

(4) Carbide can only be stored without a licence in a quantity 
not exceeding 28 pounds. 

(5) If it is desired to store larger quantities a licence must be 
obtained from the local authorities. 

(6) Carbide should be of a quality to yield not less than 4-8 cubic 
feet of acetylene per pound. 

Fig. 15 shows an airtight carbide chamber; it holds 2 cwt. 

Acetylene Generators. 

(1) See that the generator is of ample capacity for the continuous 
production, without heating, of the maximum quantity of acetylene 
required, and that it complies with all official recommendations. 

49 4 



50 



MODERN METHODS OF WELDING 



(2) See that, whether the system employed be automatic or non- 
automatic, the holder is of sufficient capacity to obviate any loss of 
gas due to production when the supply to the blowpipe is cut off. 

(3) See that the design precludes any appreciable admission of 
air to the apparatus in the charging with carbide. 

(4) See that the limit of pressure in any part of the apparatus 
does not exceed 250 inches of water. 

(5) See that the size of the pipes conveying the gas is propor- 
tioned to the maximum rate of generation. 




Fig. 15. — Airtight Carbide Chamber. 

(6) See that it is impossible to seal hermetically the generating 
apparatus. 

(7) See that no copper fittings are employed in connection with 
the acetylene apparatus. 

(8) See that all back-pressure valves are in working order as per 
regulations. 

(9) Charge the apparatus with carbide, if possible, only by day, 
and do not use small-grained carbide. 

(10) Keep the apparatus clean and in good order, and carefully 
remove all sludge from the generator before recharging with carbide. 

(11) Do not use naked lights in the vicinity of the acetylene 
apparatus. 

(12) In frosty weather never use a stove in the vicinity of the 
acetylene generator. To prevent freezing of water, it is best to 
employ a steam or hot-water coil. 



REGULATIONS 51 

(13) Employ suitable purifying material and recharge after 
1 10 cubic feet per pound of purifying material have passed through 
it; test occasionally the acetylene issuing from the blowpipe with 
a piece of nitrate of silver paper. If this is at all discoloured, it 
indicates that the purifier requires to be recharged. 

(14) See that, in all cases where an acetylene generator is em- 
ployed, an hydraulic back-pressure valve is employed between it 
and every blowpipe in use, and that it is properly filled with water. 
The small drain tap should be opened after filling, any excess of 
water being drained off. The hydraulic valve must be tested every 
day in this way before being used. 

(15) If, through a back-fire or other cause, water is discharged 
from the vent pipe, always refill the chamber, and see that the small 
drip tap is afterwards opened to draw off any excess of water. 

(16) The hydraulic back-pressure valve should be dismantled 
at regular intervals and cleaned out, to make sure that the vent pipe 
and passages are clear. 



CHAPTER XI 
BLOWPIPES 

Blowpipes intended for the autogenous welding of metals, which 
employ oxygen and acetylene as the gases, are manufactured instru- 
ments, with the same accuracy as a watch ; and they must be used 
as such with care. They are light and easy to handle, and are made 
with great skill so as to allow the correct proportions of acet3dene 
and oxygen, in specified measured volumes, at a fixed velocity, 




Section of Fouche biowpipe 



Fig. 16. — Fotjche Blowpipe, Section and Elevation. 



according to the size of the blowpipe. Their length and weight 
vary, as does their size, ranging from a consumption of 1-75 of acety- 
lene to 100 cubic feet per hour. 

The consumption of acetylene should be about 1 to 1-3 of oxygen. 
The necessary conditions are much more difficult to realise than they 
appear to be, especially with blowpipes in which the acetylene is 
admitted at the pressure of generation, which is about 8 to 12 inches 
water pressure. A great difficulty is in obtaining the requisite 
stability. A large number of details merit attention, such as ease 
of manipulation and ease of taking to pieces and reassembling. 

52 



BLOWPIPES 



53 



The velocity of propagation is about 330 feet per second in the case 
of oxygen and acetylene. In order to avoid the striking back of the 
flame it is necessary that the velocity of the mixture at the exit 



» fl 





pq 



should be of the same value, so that it prevents the return of the 
flame to the interior. The oxygen being under pressure, it is easy 
to keep this gas constant; but acetylene is not under pressure, and 
the blowpipes have to be designed to get the amount required to 
complete the correct mixture for combustion. 



54 



MODERN METHODS OF WELDING 



Low-pressure blowpipes are designed on the injector principle, 
and have separate internal jets for the oxygen fixed inside the blow- 
pipe. Such a jet has a very small hole bored in it, the size being 
determined by the size of the blowpipe for which it is to be used. 




Fig. 19. — Multiple Tips Universal Blowpipe, Small Size. 

On the outside of this inner oxygen jet is space for the acetylene, 
which is attached to a tube (usually) which runs along the pipe, where 
the rubber tubing is fixed. The oxygen under pressure rushes out 
through the small internal jet, in the place where the acetylene is; 




Fig. 20. — Multiple Tips Universal Blowpipe, Large Size. 



and the velocity of the oxygen draws the acetylene with it to the 
mixing chamber and out of the outer nozzle, in the proper propor- 
tion required for a good steady flame. Most injector blowpipes 
are designed on this principle. The intimate mixtures of the gases 



BLOWPIPES 55 

should be perfectly accomplished before they escape from the blow- 
pipe. This is difficult to attain, because it is necessary to avoid too 
much loss of pressure, which would demand an increase in the pres- 
sure of oxygen in order to regain the required A^elocity at the exit. 
This would be detrimental to the weld. 

A blowpipe, which in appearance is such a common article, 
requires such precision in construction that it can only be under- 
taken by specialists in the subject. It is essential, indeed, to leave 
to specialists and experts not only the design and construction but 
even the repair of blowpipes. Economy and good results in weld- 
ing depend largely on this. Delivery of oxygen being fixed by the 
size of the injector orifice, and the power of the blowpipe being 
invariable in these limits, therefore, in practice, variation of pres- 
sure clearly means bad welding. The makers stamp on each size 





Fig. 21. — Endazzle Blowpipe, Single Tip Pattern. 

of blowpipe the correct pressure at which it will work and give the 
best results. This pressure should not be increased. It is quite a 
common practice among welders, when their blowpipes are not 
working well, to increase the oxygen pressure with the idea of getting 
a better flame. This is a very bad practice indeed, and the weld is 
usually spoilt. Too much importance cannot be laid on this vital 
point. Manufacturers who are expert in their line would not stamp 
a working pressure on their blowpipe if it can be used for higher 
pressure. 

According to the different thicknesses of the metal to be welded, 
various sizes of blowpipes will be wanted. The pressures and 
volumes of gases required varying with the size of the welds, it is 
necessary, therefore, to have blowpipes designed to suit. They 
range, as has been said, from T5 to 100 cubic feet per hour of acety- 
lene gas. There is a great variety of blowpipes at present on the 
market — -some good, some medium, and some bad. All operators 
should make themselves fully conversant with the various designs 
and the manufacture of the same. One thing that must be remem- 
bered is that the orifice of the nozzle of any blowpipe is proportionate 



56 



MODERN METHODS OF WELDING 



to the delivery of the injector when using the pressure of oxygen 
stipulated by the makers. It is essential that it should not be 
reduced or enlarged. If it were, the gases would not be correctly 
mixed for the proper combustion for a stable flame. Almost 
the first blowpipes for low-pressure welding were made by 
Fouche, a Frenchman. These were well constructed and very 




Fig. 22. — Endazzle Blowpipe, Multiple Tip Pattern. 



reliable in working. In fact, they are still more reliable than 
many more modern ones. Their only fault was that they were 
heavy. Fig. 16 shows one in section and one in elevation. 

The "Universal" blowpipes are made by the British Oxygen Com- 
pany. They are very largely used, and are good blowpipes. They 
are standardised, and new parts for renewals can easily be got . The 



BLOWPIPES 



57 



universal blowpipes may have either a fixed or interchangeable 
head. The two kinds are practically the same in appearance and 
construction. In the interchangeable set there are loose heads of 
various sizes, with one handle only. The heads vary in power, 
and are numbered to correspond with the proper pressure required. 




**H 



Fig. 23. — Osborne Blowpipes, Four Different Types. 



The small siza is supplied with seven heads ranging from 2 to 8, 
and the larger size with four heads, representing 8, 10, 12, 15. 
These blowpipes are compact and useful. 

The blowpipe shown on p. 55, known as the "Endazzle," is ex- 
tremely light, and has a unique attachment: a pressed-steel hinged 
cover over the rubber tube connectors. These open right out to 
allow the rubber tubes to be fixed on the ends of the blowpipe, and 



58 



MODERN METHODS OF WELDING 



then afterwards close up, which prevents the hands from being 
burnt should ignition take place at the handle of the blowpijae. 
This often occurs if the tubing is not a good fit. 

The type below (Figs. 24 and 25) — injector heads with tips com- 
plete — is made in several sizes for operating on different sections of 
metals. For greater convenience these blowpipes are made in two 
models. Each model is supplied complete with directions, and each 
injector head is of proper proportions to produce the correct mixtures 
of gases and a flame of perfect stability and correct dimensions 
according to the work for which it is intended. Model A has a 
range of injector heads — sizes to 4 — that is, five different blow- 
pipes (heads only). Model B has a range of injector heads — 1 to 
9 — 'that is, nine different blowpipes (heads only). This covers a good 
range and will weld anything from T \ inch to 1 inch thick. 




Fig. 24. — Small Style C Welding Blowpipe, No. 453. 



These blowpipes, known as the Davis-Bournonville type (Figs. 
24 and 25), are provided in two standard sizes — large and small — 
which can be fitted with either square or angle heads (45, 75, 
or 90 degrees), and straight or angle hose connections; but the 
standard model is shown here. This blowpipe is very desir- 
able for light and medium sheet metal welding and light repair 
work, where a light, compact, nicely balanced tool is appre- 
ciated. Weight, 18 ounces; length over all, 14 inches. Fitted 
with five tips — Nos. 1, 2, 3, 4, 5, style 99 — using oxygen pressures 
of 2, 4, 6, 8, and 10 pounds respectively. It is used to advantage 
on metal ^V to T 5 g inch thick. 

A standard blowpipe for heavy welding, and for general 
shop work requiring a strong blowpipe. Weight, 2 pounds; 
length over all, 20 inches. Fitted with five tips — Nos. 6, 7, 
8, 9, 10, style 100 — using oxygen pressures of 12, 14, 16, 18, and 



BLOWPIPES 



59 



20 pounds respectively. This blowpipe can be used on metal 
from J inch thick upward. 

Consumption of Blowpipes. — Blowpipes of high, medium, and 
low pressures are constructed so as to give flames of all intensities 
requisite for the practice of autogenous welding. The power is 
reckoned according to the hourly consumption of acetylene. 
Some consume 1-7 to 100 cubic feet of acetylene per hour, or 20 
cubic feet, which corresponds to the hourly delivery of acetylene 
The blowpipe with the lowest consumption uses about 1 -5 cubic feet 
per hour of acetylene. This welds sheet iron or steel up to T V mcn 
thick; larger blowpipes consume 80 to 100 cubic feet of acetylene 
per hour, and these weld 1-inch thick material. 

In dealing with the consumption of acetylene, it is as well that 
we should deal with the oxygen at the same time. Theoretically 




Fig. 25. — Large Style C Welding Blowpipe, No. 146. 



we know that to get a correct mixture and a neutral flame with a 
small white cone the gases must be mixed in equal proportions — 
that is, 1 volume of oxygen, 1 volume of acetylene, when measured 
under normal temperature. Blowpipes for the high and medium 
pressures obtain this result by using the two gases under equal 
pressures, direct from the two cylinders — oxygen and acetylene. 
It is nearly approached in blowpipes in the medium-pressure 
system; but it cannot be reached in the low-pressure system. 

It is general, in ordinary works practice, to use 1 of acetylene 
to 1-3 of oxygen; it is only in well-designed blowpipes, working under 
normal conditions, well-regulated flame, without apparent excess of 
either oxygen or acetylene, and an expert welder, that these results 
are obtained. But low-pressure blowpipes give trouble if they are 
not well taken care of to prevent their getting knocked about. 
Also there are the difficulties with the regular supply of acetylene 



60 MODERN METHODS OF WELDING 

and the constant pressure. The oxygen being under pressure, 
it is difficult to mix the acetylene in absolutely accurate quantities 
in order to give it sufficient velocity. 

There is evidently an energetic mixing of the two gases, but the 
contact is not molecule to molecule, and the stream lines of oxygen 
or acetylene can escape at the nozzle without being mixed. One can 
test this in different ways — for example, by contracting the exit 
tube of the mixing chamber, or by increasing the pressure of the 
oxygen. In both cases the proportion of oxygen to acetylene is 
raised considerably. From this it is apparent that blowpipes for 
low pressure use least oxygen when the admission pressure of oxygen 
is least, and this arrangement for obtaining a mixture of the two 
gases is the best. In some blowpipes the oxygen pressure to be used 
corresponds with the arrangement of the mixing chamber. Change 
of section and abrupt bending produce a loss of pressure. One 
must find an equilibrium between the two factors, which are opposite. 
If the pressure of oxygen is not raised too high, the arrangement of 
mixing is excellent, and the result will be perfect. From prac- 
tice it is well known that, as the welding proceeds, the blowpipe 
becomes heated, and the gases, especially acetylene, expand. This 
causes a decrease in acetylene gas, and makes the flame at once 
oxidising. 

From tests which have been made upon the consumption of the 
gases by the Congress on Autogenous Welding, getting fifty blow- 
pipes from the different manufacturers (the average delivery of 
acetylene was fixed at 350 litres per hour, and the work to be executed 
lasted from thirty to forty minutes: the welders were experts), 
the best proportion of oxygen to acetylene was 1-12, the average 
1-3, and the worst 1-9. A test was also made with the same blow- 
pipe handled by two welders, one using oxygen at 28 pounds pressure 
and the other at 13 pounds. The proportion in the first case was 
1*83, in the second 1-25, showing clearly the influence of excess 
pressure of oxygen on the consumption of the gas. These tests 
prove that, according to the type of blowpipe and the conditions of 
use, the consumption of oxygen for a constant delivery of acetylene 
can vary greatly and may double in volume. Not only is the oxygen 
consumed in excess of the theoretical amount a pure loss; its pres- 
ence in the flame oxidises the metal, lowers the strength of the weld, 
and renders it brittle and porous. These considerations are im- 
portant from the point of view of economy and good work, and those 
interested should carefully study them. 

In the choosing of blowpipes many things are to be taken into 



BLOWPIPES 61 

account; if it is to be used for continuous work on one thickness of 
metal, then the proper sized blowpipe should be chosen with a fixed 
delivery. Then, again, one must satisfy oneself that one is buying 
the best article, not so much as regards appearance or shape, as 
with a view to lowest consumption for the particular size of work; 
and a guarantee should be got from the makers for a stipulated 
hourly consumption. If the class of welding is changeable from 
thick to lighter materials, then a combined independent set with all 
interchangeable heads would be most suitable. This applies to 
small equipments in small shops. On the other hand, in large shops 
where a good number of operators are empkyyed it is more economi- 
cal to have fixed ones ; they are not so delicate as the interchange- 
able, which, by the constant changing, suffer more wear. 

The actual weight is often important in practical use. Some- 
times welders say that the best blowpipes are those that are light 
in the hand; but unless they have attended instructional classes 
they have not the slightest knowledge of the consumption, or other 
details which must be settled before purchase. If the work is 
continuous, then a light blowpipe should be adopted, providing, of 
course, that the working is right, with the correct mixtures of gases 
and the consumption up to standard. If the work is heavy, such 
as some repairs which have to be done quickly, then a heavy type 
would be preferable. 

The questions of working, the consumption of the gases, and 
the maintenance in the workshop, have been badly neglected in the 
past. As competition is getting keener daily, however, manu- 
facturers are now interesting themselves in the details. One comes 
across many blowpipes which are well constructed and regulated, 
but have that tiresome striking back of the flame into the interior 
when the nozzle gets heated. This is a serious defect, because the 
welder generally increases the pressure of oxygen. 

A guarantee should be got from the suppliers that this back-firing 
will not take place. The matter of consumption is a vital point as 
regards economy and cost. In large shops, where there are one 
hundred or more blowpipes in use at once, the saving in oxygen, 
with the very best designed blowpipes, giving a consumption of 
1*3 of oxygen to 1 of acetylene, may amount to hundreds of pounds 
per year. 

The author has made tests in this direction, one of which may 
be described here. Six blowpipes were used, two each of different 
manufacture, which we call A and Al, B and Bl, C and CI. These 
tests were made on a 1-inch plate, butt-welded, with 12-gauge thick 



62 MODERN METHODS OF WELDING 

charcoal iron wire as the welding-rod. These tests lasted twenty- 
five minutes, and the following were the results : 

A and Al gave 1-3 of oxygen to 1 of acetylene. 
B „ Bl „ 14 „ „ „ 

C ,, CI ,, 1-75 f , ,, ,, 

These are clear instances of the varying makes of blowpipes, 
and it at once demonstrates how important it is to have the very 
best designed blowpipes that are made. As a further illustration : 
suppose a bad blowpipe, using 1 -75 of oxygen to 1 volume of acety- 
lene; say that the consumption of the works is 4,000 cubic feet 
per month— that is, ten cylinders of 100 cubic feet each per week 
(many firms use this quantity per hour). Under these conditions 
it would be — ■ 

^-^ = 2,971 cubic feet. 

The loss on a badly designed blowpipe is, therefore, 1,029 cubic 
feet, which, at Id. per foot, is £4 5s. 9d. per month, and £51 9s. per 
year. This is only 10 cylinders per week — for larger users, the saving 
is greater. Apart from the loss, this excess of oxygen is highly 
detrimental to the welds, which is much more serious even than the 
loss of the gas. 

Maintenance of Blowpipes. 

Users of blowpipes must bear in mind always that they are 
articles of precision. They are made on delicate lines, to be deli- 
cately used, and not to hammer the weld as the author has seen 
some operators do. If carefully protected, they will last for years, 
just the same as when new. The taking to pieces must not be done 
with cumbersome tools, and in cleaning the nozzles, copper wire 
should be used. If the orifice is in any way enlarged, the slightest 
alteration in section produces derangement. The blowpipe section 
of the nozzle corresponds to a determined flow of oxygen, but the 
orifice for the flowing of the oxygen (the injector) remains unchanged, 
and any increase of the nozzle opening brings about a decrease of the 
velocity at the exit, which provokes a return of the flame into the 
interior of the blowpipe. When welding, the oxides, or particles of 
metal, produce the following results : 

The delivery of the oxygen being variable and escaping under 
greater pressure than the acetylene, causes the flame to become 
oxidising in effect. The orifice being smaller for the passages of the 



BLOWPIPES 



63 



two gases, it is the stronger (the oxygen) that gets through in pre- 
ference to the acetylene. 

One must never allow oil or grease on the blowpipes or tubes, 
as in oxygen the oil may catch fire, and usually burns the rubber 
tube. This often happens to new blowpipes, in which the oil has 
got inside during manufacture. Do not take a blowpipe to pieces 
unless you are versed in its component parts, especially the inner 





UB 



Fig. 26. — Showing the Correct Neutral Flame, Middle One Correct. 



jet. This can rarely be adjusted again hi the same place. Before 
sending out they are adjusted to a gauge, and one-thousandth of 
an inch out in this injector sets it all wrong. The best and quickest 
method is to return it to the makers for repairs. 

If a blowpipe is obstructed by dust or other particles (generally 
lime dust carried over from the generator), these should be got away 
by fixing the rubber tube on the nozzle end of the blowpipe, leaving 



64 



MODERN METHODS OF WELDING 



the taps open and turning on the oxygen temporarily. This should 
blow it quite clean. 

All operators should take great pride in blowpipes trusted to 
their care, and should, as I have said before, treat them as instru- 
ments of precision, keeping them ranged in good order and always 
polished. 

The following are a few hints which will be found useful : 

(1) See that the blowpipe is in good order, and no passages 
obstructed; also that the rubber tubes are correct and securely 
fixed, and the regulator on the oxygen cylinder in proper working 
order. 

(2) See that you have ample acetylene and oxygen for the 
work in hand before commencing; it is injurious to the weld to stop 
in the middle. 

(3) Turn the oxygen and acetylene taps full on, and light the 
blowpipe. The flame will then probably have an excess of acetylene, 
which should be reduced by gradually turning the acetylene tap 
on the blowpipe (or the outlet of the hydraulic valve, if there is no 
tap on the blowpipe), until the flame of the blowpipe has a clearly 
defined cone at the orifice. Fig. 26 shows what is required. The 
first one has an excess of acetylene; the second is correct; and 
the third has too much oxygen. 

Blowpipes required for welding by the oxy-acetylene system 
must be chosen with care, must come up to the standard rules, and 
must not use more than 1-3 volumes of oxygen to 1 of acetylene. 
Also they must be easy of regulation, easy to handle, and able to keep 
up a regular and stable flame over long periods of working. 

The following is an approximate table, giving the consumption 
of each size of blowpipe, for oxygen and acetylene; the size of the 
blowpipe to use, with the thickness of the plate being welded, and 
the length of feet that should be welded per hour. These tables 
are very useful and should have close attention. 



Size of blowpipe 

Approximate thickness of plate- 
joint 

Approximate con-' 1 . 

sumption of[/ oxygen .. 
gases per hour! ^acetylene .. 
in cubic feet . . J 

Feet welded per hour 



2 


3 


4 


5 


6 


7 


8 


10 


12 


— 


— 


— 


i" 

8 


— 


4 


3* 

8 


X" 


3" 
4 


1-7 
1-2 


3 
2 


6-5 
4-3 


9 
6-3 


16 
11 


23 
16 


34 

24 


48 
34 


75 
48 


40 


30 


20 


15 


12 


9 


7 


H 


2| 



15 

1" 

100 

70 



H 



CHAPTER XII 
FLEXIBLE TUBING 

No welding installation is complete without the means to conduct 
the gas from the oxygen cylinders and the hydraulic valves. The 
gas is conveyed by rubber tubing fixed on the proper connectors, 
attached to, firstly, the blowpipe; secondly, the hydraulic safety 
valve; and thirdly, the regulator on the oxygen cylinder. This 
rubber tubing is very important in any installation, and unless great 
care is taken by the welders, and the best quality of rubber purchased, 
it is an expensive maintenance charge. A cheap quality of rubber 
tubing is useless. Some of that on the market contains much more 
loading material than rubber. Such is dear at any price, although 
in appearance there is not much to choose. The best tubing con- 
sists of a good, soft, pliable inside rubber liner, of good stout thickness 
and not less than f inch inside clear diameter, reinforced by at 
least three-ply heavy woven canvas. It must suit the connectors 
on the blowpipes, regulators, and hydraulic safety valves. The fit 
should be just sufficient to secure a gas-tight joint at the connectors, 
but not too tight, so that it can be removed without undue strain 
or stretching of the tubing. There are 60 lineal feet in each coil 
of rubber tubing, and these usually cut into four pieces, making the 
requirements for two operators for two 15 feet each, one for the 
acetylene and one for the oxygen. 

This rubber tubing is badly abused in the workshop. It is often 
blown open by the welders suddenly turning the oxygen on full at 
high pressure when the blowpipe tap is closed. Also at times they 
burn the tubing whilst welding, unknown to themselves. Itmayget 
accidentally thrown across the hot article which is being welded, 
and usually this is not found out till a hole has been burnt in it. 
Again, the tubing frequently gets cut by articles dropped on to it. 
On making an examination on the tubing being used, it will often 
be found that one sample in five is leaking, and the oxygen blowing 
away in the atmosphere. This is a costly item and should be 
watched very closely. Often, too, the tubing ignites at the connec- 
tor of the blowpipe, because the rubber liner is curled up inside 

65 5 



66 MODERN METHODS OF WELDING 

and does not make a gas-tight joint; consequently, the oxygen 
escapes. The welder, not aware of this, continues welding till a 
spark flashes from the weld and ignites the rubber tubing at the 
connector of the blowpipe. It becomes incandescent immediately, 
probably burning the operator's hand, unless he is quick enough 
to drop the lighted blowpipe. It is necessary to have tubing of the 
correct size to fit the connectors, so as to avoid the bad practice of 
tying with wire. 

Neither the connector nor the rubber should have any grease 
or oil on it. This will set up instant combustion if any oxygen 
catches it. If the end of the tubing is hard to get on, it should be 
dipped in water. This will ease the fixing on of the connectors. 
All connections, unfortunately, are not alike, which makes the fitting 
of tubing awkward where the connectors vary. It would be a great 
boon if all manufacturers of these connections were to standardise 
the sizes. It would cheapen production, and save much time lost 
in trying to get one size tubing on another size connector. For 
cutting blowpipes, the rubber tubing must be very much stronger, at 
least five-ply, owing to the greater pressure required for cutting iron 
and steel. 

In many cases, when cutting very thick plate at high pressures, 
armoured tubing must be used. 

The connectors on the blowpipes, regulators, hydraulic safety 
valves, should all be painted with shellac : this assists in keeping the 
tubing on without using wire, and makes a tight joint. 

The present system of connectors for the rubber tubing is 
not very satisfactory, and new ones ought to be brought into service. 
These new ones consist of a union joint with coupling, so that one 
half of the union can be fitted on the gauge on the cylinder, and the 
other half fitted on the rubber tubing at the gauge end. These 
union couplings should also be attached to the hydraulic safety valve, 
and at the other end of the tubing to that which is attached to the 
gauge on the cylinder, and the same union couplings on the blowpipe. 
The great advantage is that half the coupling is fixed permanently 
on each end of the tubing, thereby saving much time and preserv- 
ing tubing. 



CHAPTER XIII 
SAFETY VALVES 

It is a well-known fact that oxygen and acetylene are very highly 
explosive, and it is indispensable that all precautions should be 
taken to prevent the formation of these combustible gases. Their 
use is becoming more and more general in every part of the country, 
and we have therefore to put forward continually that precautions 
must be taken to prevent their formation, especially as their inflam- 
mation is very easily produced. With acetylene in use at a lower 
pressure than oxygen, the oxygen can return in the acetylene tubes 
and piping and so combine this gas in the generator. This occurs 
when there is a partial obstruction of the blowpipe, caused often by 
the welder allowing the blowpipe suddenly to touch the molten metal. 
The oxygen, being under pressure, and as the outlet is blocked, 
flows up the acetylene tube into the safety valve or hydraulic seal. 

Therefore it is absolutely essential to place in the acetylene 
piping, between the generator and the rubber acetylene tubes on the 
blowpipes, an arrangement capable of arresting immediately any 
return of the oxygen. The object of a safety valve is to direct into 
the open air any oxygen which returns in the direction of the acety- 
lene. It is not really meant to stop back-fire, but to prevent forma- 
tion of a mixture of high explosive gases by the return of the flame. 

The efficacy of such an apparatus must be absolute. So far a 
simply designed water seal has proved the most effective. It is one 
that cannot go wrong if the water level is kept right. In the hydrau- 
lic safety valve, two tubes emerge from a layer of water, one for the 
entry of the gas and the other open to the exterior, placed at different 
levels, constituting an absolute barrier against all return of the 
oxygen in the acetylene piping. Other arrangements, not based 
on this principle, should be rejected. 

The illustration (Fig. 27) shows a good standard type made by 
the British Oxygen Company. The acetylene pipe from the gas- 
holder or main supply is connected with tap A, and the acetylene 
tube leading to the blowpipe is connected with tap B. C is a loosely 
fitting lid, covering the cup in which the water is poured to charge 

67 



68 



MODERN METHODS OF WELDING 



the seal pot D up to the level of the tap E. Taps A and B must be 
closed whilst the seal pot D is being charged with water. When 
water shows at tap E, immediately stop filling, and, allowing time 
for the surplus water to drain off, close the tap E. The lid C must 





Fig. 27. — Safety Valve, Elevation and Sectional. 

then be replaced, and the taps A and B may be opened. The valve 
is then in working order. 

The filling pipe F is made long enough to hold a column of water 
greater than the pressure of the acetylene generator. There should 
not be less than 8 inches of water. When at work the taps A and B 
must be open, and the supply of acetylene regulated by the tap on 
the blowpipe. Should the blowpipe nozzle at any time become 



SAFETY VALVES 



69 



choked whilst the oxygen supply remains unchecked, the gas would 
be forced by its superior pressure along the acetylene tube. The 
back pressure thus caused, acting on the surface of the water in the 
seal pot D, would seal the acetylene pipe and force the water up the 
pipe F, displacing the liquid 0. The hydraulic seal to the atmo- 




Fig. 28. — Standard Sectional Type Safety Valve. 



sphere would thus be destroyed and both gases would escape until 
taps A and B were closed. Thus oxygen can never penetrate the 
acetylene supply beyond the hydraulic valve, provided the valve 
is kept properly filled. 

There is really very little scope for modification in the design 
of these hydraulic valves. Two conditions, however, are essential 



70 MODERN METHODS OF WELDING 

— viz., that the pipe conveying acetylene from the generator dis- 
charges into the water seal pot at a lower level than the opening to 
the vent ; and that the vent pipe has a direct vertical discharge from 
the seal pot into the atmosphere. 

All hydraulic back-pressure valves must be fixed on the acetylene 
supply pipe in a vertical position, as near to the blowpipe as con- 
venience will permit. A good position is on a wall, with the bottom 
of the valve about 4 feet from the ground. The acetylene inlet pipe, 
coupled to the tap A, should extend vertically several feet above the 
tap. In cases where two or more blowpipes are worked from the 
same acetylene supply a separate hydraulic back-pressure valve 
should be employed for each. 

One must be very careful in the choice of hydraulic back-pressure 
valves. A serious explosion, resulting in grave injuries to more than 
one workman and the total destruction of an acetylene generator, 
occurred in a munition works in Yorkshire in May, 1917. The holder 
formed part of a large plant which had been in successful operation 
for several years. Suspicion not unnaturally attached itself to the 
hydraulic valve. 

No part of an oxy-acetylene outfit is more important or requires 
more careful attention than the hydraulic back-pressure valve. 
The explosion in question was caused by a badly designed hydraulic 
back-pressure valve of German make, in which there was a U-tube 
fitted, one end of which was fixed in the seal pot, and the difference 
between the U-pipe and the supply pipe was not sufficient to make a 
satisfactory seal. It is obvious that such a valve as this is useless 
as the means of preventing oxygen, at its superior pressure, from 
flowing back to the acetylene generator. The essential method of 
working is for the acetylene to bubble through a small height of 
water, which is nevertheless sufficient for covering the tube leading 
to the exterior, this being between the surface of the water and the 
level of the escaping acetylene. The valves must not be too large 
a gas capacity. The diameter of the body should just be suffi- 
cient to retain the level of the water constant, and the height enough 
to avoid drops of water reaching the outlet of the acetylene. The 
pipe which comes from the main supply into the seal pot should be of 
suitable diameter for maximum delivery to the largest blowpipe, 
so as to avoid all loss of pressure. 

Often a pipe of small diameter, when a large blowpipe is used, 
causes eddies in the flow of the gas, through the delivery not being 
sufficient. The pipe which leads from the generator should go 
through the seal pot to within \ inch of the bottom. The bottom 



SAFETY VALVES 71 

end of this should be shaped in the form of a cone, and the cone should 
have small holes drilled in it to allow the gas to spread more when 
passing through the water. The height of the water in the seal pot 
should be about 3 inches clear of the top holes in the cone. This 
will be the position of the test tap. The acetylene outlet tap will 
be about 8 inches above this. The atmosphere pipe should be placed 
half-way between the test tap and the holes of the inlet acetylene pipe. 
The height of this pipe depends on the pressure of the acetylene, 
since the water rises in this tube as the pressure of the gas is in- 
creased. The height should be related to the level of the water in 
the valve, and should be more than the greatest possible pressure 
that would be used in the generators. 

The illustration (Fig. 28) shows a valve that is infallible in working 
and is simple in construction. It can easily be made by any in- 
telligent man. It consists of one piece of solid drawn tube, 3 inches 
inside diameter, with discs welded top and bottom. The bottom 
disc should have a quarter gas socket welded on, to take a tap to 
drain the water out when this is required for cleaning purposes. 
Gas sockets may also be welded at each of the tap holes for screwing 
them in. The acetylene inlet tube and the filling tube may both be 
welded in the disc top before welding the top on ; but one must be 
careful to get the tubes fixed at the proper depth before welding 
them in. 

The outside tube terminates in a funnel, which is used for filling 
the valve with water. This is covered by a lid. Well-designed and 
well-constructed hydraulic valves work well, are safe, and do not 
get out of order. It is only necessary to verify the level of the water 
daily, or every time it is left standing, and all operators should see, 
and make a practice of, trying the test tap not less than twice a day. 



CHAPTER XIV 

PURIFIERS 

Purifiers generally consist of cylindrical vessels, usually made of 
sheet steel with an airtight lid or cover. They usually contain a 
series of trays holding the purifying materials. The calcium carbide, 
as now manufactured, is by no means a chemically pure substance. 
It includes a large number of foreign bodies. In crude acetylene, 
these are partly gaseous, partly liquid, partly solid. They may 
render the gas dangerous from the point of view of possible explo- 
sions. They, or the products derived from them on combustion, 
may be harmful to the health if inhaled. They are objectionable 
at the burner orifices, by determining, or assisting in, the defects of 
the metals of the weld. 

A proper system of purification is one that is competent^ to 
remove the carbide impurities from the acetylene, as far as that 
removal is desirable or necessary. The generator impurities, as 
stated above, are oxygen, nitrogen, and lime in the form of fine dust. 
This lime may be extracted when the gas is passing from the genera- 
ting chambers along the outlet pipe and down again through the bent 
pipe which dips in the water of the tank. As the gas bubbles through 
the water, part of the lime dust is removed. What escapes extrac- 
tion may be removed by passing the gas through cotton- wool or felt, 
which is usually placed over the purifying material, in the top of the 
purifier. 

The least volatile liquid impurities will be removed partly in the 
condenser (if one is fixed), partly in the washer (the tank), and 
partly by mechanical dry-scrubbing action of the solid purifying 
material in the chemical purifier. Sufficient removal of these genera- 
tor impurities need throw no appreciable extra labour upon the con- 
sumer of acetylene, for one can readily select a type of generator 
in which the production is reduced to a minimum, using a cotton- 
wool or coke filter for the gas. A water washer, which is very useful 
in the plant, if only employed as a non-return valve between the 
generator and the main piping and the indispensable chemical puri- 

72 



PURIFIERS 73 

fiers, will take out of the acetylene all the remaining generator im- 
purities which need to, and can, be extracted. 

In designing a washer for the extraction of the ammonia and 
sulphuretted hydrogen, it is necessary to see that the gas is brought 
into most intimate contact with the liquid, while no more pressure 
than can be avoided is lost. One volume of water only absorbs 
about 3 volumes of sulphuretted hydrogen at atmospheric tempera- 
ture, but takes up some 600 volumes of ammonia ; and, as ammonia 
always accompanies the sulphuretted hydrogen, the latter may be 
said to be absorbed in the washer by a solution of ammonia, a liquid 
in which sulphuretted hydrogen is much more soluble. Since the 
water only dissolves about an equal volume of acetylene, the liquid 
in the washer will continue to extract ammonia and sulphuretted 
hydrogen long after it is saturated with the hydrocarbon. To avoid 
waste of acetylene by dissolution in the clean water of the washer, 
the plan is sometimes adopted of introducing water into the genera- 
tor through the washer so that, practically, the carbide is always 
attacked by a liquid saturated with acetylene. For compactness 
and simplicity of parts, the water of the holder seal is often used as 
a washing liquid. But unless the liquid of the seal is constantly 
renewed it will become offensive, and will act corrosively on the 
metal of the tank and bell. 

The reason why the carbide impurities must be removed from 
acetylene is this: There are three compounds of phosphorus, all 
termed phosphuretted hydrogen or phosphine — a gas PH 2 , a liquid 
P 2 H 4 , and a solid P 4 H 2 . The liquid is spontaneously inflammable 
in the presence of air — -that is to say, it catches fire of itself, without 
the assistance of a spark or flame, immediately it comes in contact 
with the atmospheric oxygen. Being very volatile, it is easily 
carried away as vapour by any permanent gas. In commercial 
carbide it has been found that the highest amount of phosphine in 
the acetylene is 2-3 per cent., and this gas is capable of self -inflamma- 
tion. Bullier states that acetylene must contain 80 per cent, of 
phosphine to render it spontaneously inflammable. 

Ammonia is objectionable in acetylene because it corrodes the 
brass fittings and pipes, and because it is partly converted into 
nitrous and nitric acids as it passes through the flame. 

Sulphur is objectionable in acetylene because it is converted 
into sulphurous and sulphuric anhyhrides, and their respective acids, 
as it passes through the flame. 

Phosphorus is objectionable because, in similar circumstances, 
it produces phosphoric anhydride and phosphoric acid. Each of 



74 



MODERN METHODS OF WELDING 



these acids is harmful to the human system, sulphuric and phos- 
phoric anhydrides (S0 2 and P 4 O 10 ) acting as a specific irritant to 
the lungs of persons predisposed to affections of the bronchial 
organs. 

Phosphorus, however, has a further harmful action. Sulphuric 
anhydride is an invisible gas, but phosphorous anhydride is a solid 
body, and is produced as an extremely fine, light, white, voluminous 
dust, which causes a more or less opaque haze. Phosphoric anhy- 
dride is also partly deposited in the solid state at the burner orifice, 




Fig. 29. — Purifier, showing Section and Elevation with Purifying Material. 



and, always assisting in the deposition of carbon from any poly- 
merised hydrocarbon in the acetylene, thus helps to block up 
and distort the orifices of the blowpipes. 

Purifiers are usually made from sheet iron or steel and galvanised, 
and often in good plants contain a porcelain vessel for holding the 
purifying materials, as acid from some of these act on the mild 
steel shell, corroding it. Fig. 29 shows a purifier made from sheet 
steel, in which all the joints are welded, and the connecting pipes 
also welded in ; the purifying material is put into trays, the bottom 
of which is perforated with small holes. The lowermost tray is set 
about 3 inches from the bottom, the other trays on the top of this, 



PURIFIERS 



75 



leaving a space of about | inch between each tray. In the bottom 
of each tray is a layer of thin felt, to prevent the purifying material 
from passing through the holes and, secondly, to act as drier for 
the gas. On the top of all the trays is a layer of felt or cotton-wool, 
put in to extract the lime dust which has not been extracted by 
the water filter, and which came over with the gases. This dust 
is thereby prevented from getting into the blowpipe or the weld. 

The purifying material should be lightly placed in the trays 
so as to allow the gases to go freely through the material without 
choking. It is usual for the inlet pipe to be at the bottom, and the 




Fig. 30. — Atox Purifier. 



outlet pipe at the top, and a water tap must be placed at the bottom 
to allow the water from condensation to be run off from time to 
time. It is important that this be tried frequently, as the water 
may be sufficient to rise up, and through the purifying material, 
thereby nullifying its properties. The purifier may be placed any- 
where between the generator and the main piping, but it is usually 
near the generator. 

In the systematic purification of acetylene the practical question 
arises, How is the attendant to tell when the purifiers approach 



76 MODERN METHODS OF WELDING 

exhaustion and need recharging? Heil has stated that the purity of 
the gas may be judged by its atmospheric flame given by a Bunsen 
burner. Pure acetylene gives a perfectly transparent, moderately 
dark blue flame, which has an inner cone of pale yellowish-green 
colour, whilst the impure gas yields a longer flame of an opaque 
orange-red tint with a bluish-red inner cone. It must be noted, 
however, that particles of lime dust in the gas may cause the atmo- 
spheric flame to be reddish or yellowish (through the action of calcium 
or sodium), quite apart from the ordinary impurities. 

The simple method of ascertaining, definitely, whether a purifier 
is sufficiently active consists in the use of test papers prepared to the 
prescription of G. Keppler. These papers are cut to a convenient 
size, are put up in book form, and may be torn one at a time. In 
order to test whether the gas is sufficiently purified, one of the papers 
is moistened with hydrochloric acid of 10 per cent, strength, and the 
gas issuing from the blowpipe, or pet eock, is allowed to impinge 
on the moistened part. The original black or grey colour of paper 
is changed to white if the gas contains a notable amount of impurity, 
but remains unchanged if the gas is adequately purified. 

The Keppler test papers turn white when the gas contains either 
ammonia phosphine, siliciuretted hydrogen, sulphuretted hydrogen, 
or organic sulphur compounds, but for carbon disulphide . that 
change is slow. Thus the paper serves as a test for all impurities 
likely to occur in acetylene. The paper is a specially prepared black 
porous kind which has been dipped in a solution of mercuric chloride 
(corrosive sublimate) and dried. These papers can be obtained, 
put up in case with a bottle of acid for moistening them as required, 
from E. Merck, 16 Jewry Street, London, E.C. 3, or from the usual 
retail dealers in chemicals. 

The sensitiveness of the test is quick. If a distinct white mark 
appears on the moistened paper when it is exposed for five minutes 
to a jet of acetylene, the latter is inadequately purified. If the gas 
has passed through a purifier this test indicates that the material 
is not efficient, that the purifier needs recharging. 

The British Acetylene Association has issued the following set of 
regulations as to purifying materials and purifiers for acetylene : 

(1) The purifying material shall remove phosphorus and sulphur 
compounds to a commercial degree — e.g., not to a greater degree 
than will allow easy detection of escaping through its odour. 

(2) The purifying material shall not yield any products capable 
of corroding the gas mains or fittings. 

(3) The purifying material shall, if possible, be efficient as a 



PURIFIERS 77 

drying agent, but the Association does not consider this absolutely 
necessary. 

(4) The purifying material shall not, under working conditions, 
be capable of forming explosive compounds or mixture. It is under- 
stood, naturally, that this condition does not apply to the un- 
avoidable mixture of the acetylene and air formed when charging 
the purifier. 

(5) The apparatus containing the purifying material shall be 
a simple construction and capable of being recharged by an in- 
experienced person without trouble. It should be so designed as to 
bring the gas into proper contact with the material. 

(6) The containers and purifiers should be made of such materials 
as are dangerously affected by the respective materials used. 

(7) No purifier should be sold without a card of instructions 
suitable for hanging up in some prominent place. Such instructions 
should be of the most detailed nature, and should not presuppose 
any expert knowledge whatever on the part of the operator. 



CHAPTER XV 
SELECTION AND INSTALLATION 

It is not possible to give a direct answer to the question as to which 
is the best type of acetylene generator. There are no generators 
made by responsible firms which are not safe. Some are easier to 
charge and clean than others. Some require more frequent atten- 
tion. Some have moving parts less likely to fail, or none at all to 
go wrong. There are contact apparatus on the market which appear 
to give little trouble. There is very little to choose, from the chemi- 
cal and physical view, between the generators now on the market. 
A selection may rather be made on mechanical grounds. 

The generator must be well able to produce gas as rapidly as 
ever it will be required during the longest time the blowpipe may 
be used. It must be strong and able to bear careless handling and 
frequent rough manipulation of its parts. It must be built of sound 
material, and galvanised after manufacture, so that it will not rust 
in a few years. Each and every part must be accessible, and its 
exterior visible. Its pipes for the gas must be large bore. The 
number of cocks, valves, and moving parts must be reduced to a 
minimum. It must be easy to clean, the waste lime must be readily 
removed. It must be so fitted with vent pipes that the pressure 
can never rise above that at which it is supposed to work. Appara- 
tus that claims to be automatic should be perfectly automatic, 
the water or the carbide feed being locked automatically before the 
carbide store, the decomposing chamber, or the sludge cock can be 
opened. 

The generating chamber must always be in communication with 
the atmosphere through a water seal vent pipe, the seal of which, 
if necessary, the gas can blow at any time. All apparatus should be 
fitted with rising holders, and the larger the better. The best place 
for a generator is in the open air, or a simple open shed, if well venti- 
lated. The diameter of the mains and service-pipes for an acetylene 
installation must be such that the main or pipe will convey the 
maximum quantity of gas likely to be required to feed properly all 
the blowpipes which are connected to it, without an excessive actua- 

78 



SELECTION AND INSTALLATION 79 

ting pressure being called upon to drive the gas through the main 
or pipe. 

The practical question in gas distribution is, What quantity of 
gas will a given actuating pressure cause to flow along a pipe of given 
length and given diameter ? The solution of this question allows 
of the diameter of the pipes being arranged so far that they carry 
a required quantity of gas a given distance under the actuating 
pressure that is most convenient or appropriate. In order to avoid, 
as far as possible, expenditure and labour in repeating calculations, 
tables have been drawn up from Morel's formulae, which will 
serve to give the requisite information as to the proper sizes of pipes 
to be used in the cases likely to be met with in ordinary practice. 

Piping used for the distribution of acetylene must be sound in 
itself, and the joints perfectly tight. Ordinary gas barrel is not good 
enough. Joints for acetylene, like those for steam or high-pressure 
water, must be made tight by using well-threaded fittings, so as to 
secure metallic contact between pipe and socket. Acetylene service 
should, wherever possible, be laid with a fall, which may be very 
slight, towards a small closed vessel adjoining the gas-holder or 
purifier, in order that water deposited from the gas through condensa- 
tion of aqueous vapour may run out of the pipe into that apparatus. 
Where it is impossible to secure an interrupted fall in that direction, 
there should be inserted in the service pipe at the lowest point of each 
dip it makes, a short length of pipe turned downwards and termina- 
ting in a plug or sound tap, to remove the condensed water. 

When all the fittings have been connected, the whole system of 
pipes must be tested by putting it under a gas (or air) pressure of 
9 to 12 inches of water, and observing on an attached pressure-gauge 
whether any fall in pressure occurs within fifteen minutes after the 
main inlet tap has been shut. The pressure required for this can be 
obtained by weighing the holder. If the gauge shows a fall of pres- 
sure of I inch or more in these circumstances, the pipes must be 
examined until the leak is located, but it must never be searched 
for with a light. Fittings for acetylene must have perfectly sound 
joints and taps — common gas fittings will not do; the joints, taps, 
ball sockets, etc., are not ground accurately enough to prevent 
leakage. Fittings are now being specially made for acetylene, 
which is a step in the right direction. 

The conditions which a generator should fulfil before it can 
be considered safe are a3 follows : 

(1) The temperature in any part of the generator when run at 
the maximum rate for which it is designed, for a prolonged period, 



80 MODERN METHODS OF WELDING 

should not exceed 130° C. This may be ascertained by placing short 
lengths of wire, drawn from fusible metal, in those parts of the 
apparatus in which heat is likely to be generated. 

(2) The generator should have an efficiency of not less than 90 
per cent., which, with carbide yielding 5 cubic feet per pound, would 
imply a yield of 4-5 cubic feet of gas for each pound of carbide used. 

(3) The size of the pipes carrying the gas should be proportional 
to the maximum rate of generation, so that undue back-pressure 
from throttling may not occur. 

(4) The carbide should be completely decomposed in the appara- 
tus, so that the lime sludge discharged from the generator shall be 
incapable of generating more gas. 

(5) The pressure at any part of the apparatus, on the side of the 
holder, should not exceed that of 250 inches of water, and on the 
service side of same, or where no gas-holder is provided, should not 
exceed 200 inches of water. 

(6) The apparatus should give no tarry or other heavy condensa- 
tion products from the decomposition of the carbide. 

(7) In the use of a generator, regard should be had to the danger 
of a stoppage of the passage of the gas, and the resulting increase 
of pressure which may arise from the freezing of water. Where 
freezing may be anticipated, steps should be taken to prevent it. 

(8) The apparatus should be so constructed that no lime sludge 
can gain access to any pipes intended for the passage or circulation 
of water. 

(9) The air space in a generator before charging should be as 
small as possible. 

(10) The use of copper should be avoided in such parts of the 
apparatus as are liable to come in contact with acetylene. 

(11) Notice to be fixed on the generator house door — " No naked 
lights or smoking allowed." 

(12) No repairs to, or alterations in, any part of a generator, 
purifier, or other vessel which has contained acetylene shall be 
commenced, nor, except for recharging, shall any such part or vessel 
be cleaned out, until it has been completely filled with water, so as to 
expel any acetylene or mixtures of air and acetylene which may 
remain in the vessel and may cause a risk of explosion. 

Having described various forms of the items which go to form 
a well-designed acetylene installation, it may be useful to recapitu- 
late briefly, with the object of showing the order in which they should 
be placed. From the generator the gas passes into a condenser to 
cool it and remove any tarry products. Next it enters a washing 



SELECTION AND INSTALLATION 81 

apparatus filled with water to extract water-soluble impurities. 
If the generator is of the carbide-to-water pattern, the condenser 
may be omitted, and the washer is only required to retain any lime 
froth and to act as water seal or non-return valve. If the generator 
does not wash the gas, the washer must be large enough to act effi- 
ciently as such, and between it and the condenser should be put a 
mechanical filter to extract the dust. From the washer the acety- 
lene travels to the holder. From the holder it passes through one 
or two purifiers, and then travels to the drier and the filter. If the 
holder does not throw a constant pressure, or if the purifier and the 
drier cause irregularities, a governor or regulator must be added 
to the drier. The acetylene is then ready to enter the service. 
When the gas generally leaves the generator house, a full-way stop- 
cock must be put in the main. 

Generator Residues. 

According to the type of generator employed, the waste product 
removed therefrom varies from a moist powder to a thin cream or milk 
of lime. Any waste product which is quite liquid in its consistency 
must be completely decomposed and free from particles of calcium 
carbide of sensible magnitude. In the case of more solid residues, 
the less fluid they are the greater is the improbability (or the less 
is the evidence) that the carbide has been wholly spent with the 
apparatus. Imperfect decomposition of the carbide inside the 
generator not only means an obvious loss of economy, but its pres- 
ence among the residues makes careful handling of those essential 
to avoid accidents, owing to a subsequent liberation of acetylene 
in some unsuitable and, perhaps, closed situation. A residue which 
is not conspicuously saturated with water must be taken out of the 
generator-house into the open air and flooded with water, being left 
in some uncovered receptacle for a sufficient time to ensure all the 
acetylene being drawn off. A residue which is liquid enough to 
flow should be run directly from the draw-off cock of the generator 
through a closed pipe to the outside, where, if it does not discharge 
into an open conduit, the waste pipe must be trapped, and a ventila- 
ting trap provided so that no gas can blow back into the generator- 
house. 

As the acetylene is now brought through in the mains, it will 
be distributed to the operators through an lrydraulic safety valve 
and rubber tubing to the blowpipes. It is usual to fix the main 
piping overhead, from which pipes are suspended, at specified dis- 
tances, upon which pipes are attached an hydraulic safety valve. 



82 MODERN METHODS OF WELDING 

It is necessary for each welder to have one hydraulic safety valve, 
or water seal, for each blowpipe. There should be welding tables 
or benches fixed running under the main piping. These tables 
or benches are generally constructed of iron or steel frames, with 
boiler-plate tops, and are made wide enough to allow welders to work 
opposite each other, therefore economising space. The arrangement 
of hydraulic safety valves is suspended from the main pipe, above 
the centre of the welding table, making it convenient and handy 
for the operators. 

The next operation is to fill all the hydraulic safety valves with 
water until it runs out of the water-level test cock. When this has 
been done, the rubber tube may be fixed to the outlet tap of the 
hydraulic safety valve at the one end, and the blowpipe at the 
other end. Then another piece of tubing is taken and fixed on to 
the regulator (which is already fixed -into the cylinder valve); 
the other end of the tubing to be fixed on to the oxygen tap of the 
blowpipe. All is now ready for the gases for welding. The acety- 
lene should be turned on at the main cock or tap. After the genera- 
tor has been charged with a proper quantity of calcium carbide, 
the holder filled with water, and the purifier charged, all should be 
ready for the acetylene to be let into the main piping. Pure acety- 
lene will not come through to the blowpipe on the first starting up 
of the plant, owing to a quantity of air in the piping and bell, 
which has to be replaced by the acetylene as soon as generation 
takes place. Before starting generation, all the taps or cocks 
fixed in the main pipes should be left open to allow the air to 
escape as the acetylene starts to come through; as the acetylene 
has a very pungent smell, it can soon be observed when it begins 
to come through in quantities. As soon as this period arrives, the 
taps can all be shut off, and the blowpipe lit. The oxygen being on 
at the cylinder and regulator, and acetylene turned on at the 
hydraulic safety valve, and then the two taps on the blowpipe — 
the oxygen first and the acetylene after the blowpipe is lit — allow 
it to burn until a good white rigid cone appears. This will take 
some time, owing to the fact that at first starting up (as already 
explained) the main piping is partly full of air, although the 
taps on the main piping have been previously opened. This air 
mixes with the acetylene, ignites at the tip of the blowpipe, and 
gives a bluish flame almost like a Bunsen burner. The blowpipe 
is to remain lighted until the flame reaches a small violet-whitish 
jet of very clear outline, when it will indicate that the air is all out 
of the piping, and welding may be done. 



CHAPTER XVI 
METHODS OF WELDING 

The subject to which we are now about to proceed is one which should 
be very interesting to welding operators. My experience, through- 
out years of instruction of operators, is that they invariably want 
to handle a blowpipe before they have even the smallest information 
of welding or what it means. They soon find out, however, that it- 
is best to start from the beginning. 

With all appliances in order, and the blowpipe chosen, work can 
be proceeded with. The pieces to be welded consist of two pieces of 
angle iron, which are put on the top of the loose bricks on the weld- 
ing table. The hydraulic safety valve is tested. The acetylene gas 
is turned on at the tap of the safety valve (the taps on the blowpipes 
being closed), then the taps on the regulator and the blowpipe are 
both opened and left open. The cylinder valve is open to let the 
oxygen through to the blowpipe. The oxygen should be turned 
off temporarily on the regulator until everything is ready and com- 
plete for welding, then the blowpipe may be lit, and the flame regu- 
lated. The blowpipe should be held in the hand, in the central 
position found by balancing. The weight of the rubber tubes will 
make the blowpipe feel balanced and light in the hand. 

When commencing welding, the blowpipe should be pointing to 
the line of welding at a slight angle, so that the blowpipe will melt 
the metal in advance of the tip of the flame. One must not hold it 
at too large an angle, otherwise the molten metal will be blown on 
the cold surface. This point or tip of the flame — that is, the clear 
white cone — must not touch the metal, but must be about i inch 
from it. This prevents oxidisation of the metal, and also prevents 
the nozzle of the blowpipe from being filled up with metal which is 
blown up with sparks. Further, a much neater weld is made with 
the flame above the molten mass than in it. 

The blowpipe should be held freely in the hand, and the weld 
approached at one edge, care being taken that, as soon as the point 
of melting has been reached, the blowpipe shall be moved slowly for- 
ward to melt, say, £ inch from the edge. After the melting of this 

83 



84 MODERN METHODS OF WELDING 

second part, the blowpipe should be instantly passed over the edge 
to weld this, which process, from the previous heating, should be 
almost instantaneous. The object of heating the edge first and 
not welding, is to stop the molten metal from running from the edge. 
Nearly all operators, when learning, make this mistake. If, as 
directed, the second part is made molten and welded, and then the 
blowpipe is brought over to the end of the weld, this becomes molten, 
the blowpipe is moved to the third position, the film on the edge 
of the plate is not broken. Hence it supports the molten of the 
edge which has been done at the second heating. When proceeding 
with the welding the blowpipe must be moved forward very slowly, 
with a gyratory movement. The progress must be regular and con- 
tinuous, so that the welding may be even and quickly done; and 
care must be taken that no welding shall be gone over twice, as each 
time it is done the metal loses some of its niost important constituents 
and it is therefore burnt and weak. If it is necessary that the two 
edges of the article that is being welded shall be made molten 
together, the welding-rod used must also be in the same molten 
mass together. If the welding-rod is kept in close proximity to the 
cone of the flame, unity of fusion of both the edges of the weld 
and the welding-rod will take place, leaving an homogeneous weld. 
It is best to train the hand, when engaged on small work, to 
make the flame of the blowpipe describe an elliptical movement, 
the longer diameter corresponding to double the width of the 
section of the article being welded. Also, at the same time that this 
is being performed, it is necessary to combine with this elliptical 
motion an advancing one ; and, in the advancing, one must keep to 
the centre line of welding. In the welding of thick plates, where 
the article is either bevelled on one side or on both, the same ellipti- 
cal and advancing movement as for light work is required; but a 
welding-rod is to be used constantly and regularly, so as to fill up 
the part that has been bevelled. In articles more than § inch thick 
two layers have to be put on, one after the other, otherwise a sound 
weld could not be secured. 

The welding-rod is held and directed by the left hand, and should 
be suspended between the top of the two fingers and the thumb, 
and over the side of the hand, almost as one holds a pen. It will be 
found that the rod will thus be balanced nicely for working with 
accuracy under the tip of the cone. The thickness of the welding-rod 
should be in proportion to the thickness of the article to be welded. 
It is very important, as previously stated, that the melting of the 
feeding-rod and the edges of the weld should take place at the same 



METHODS OF WELDING 85 

time, so as to make the edges of the article and the feeding-rod com- 
bine and form one solid metal. Particular care must be taken to 
prevent the flowing metal from the rod falling on the unwelded edges 
of the article. This would cause the weld to be defective. It would 
be adhesion, not a weld. This, although so simple an error, is often 
committed, even by experienced welders. More care ought to be 
taken not to let these simple errors occur. No matter how well 




Butt Joint. 



the other part of the weld is finished, if there is a defect like that of 
adhesion, it ruins the whole weld. In testing, the least sectional 
area will be taken. Therefore, if the article is J inch thick, and adhe- 
sion is carried for J inch deep, the weld is only half as strong. The 
smallest sectional area is \ inch thick, whereas the article is \ inch 
thick, being a loss of strength of 50 per cent. Operators should 




Fig. 32. — Indents, not Sufficient Welding-Rod on. 

make these small tests themselves, as this is the quickest and surest 
method of finding out their own defects. 

The operator should make the rod melt at the same time as the 
welded edges. The rod is kept in the proximity of the flame, at 
almost melting-point, so that, as the two edges become melted, the 
rod is put or dropped on to the molten mass, by passing just through 
the cone; and, as the welding proceeds at a uniform speed, the rod 
is progressively worked at a sufficient rate of melting, to fill up the 
gap in the bevel and to complete the level of the weld to the same 
thickness as the article being welded. If operators will keep in 



86 MODERN METHODS OF WELDING 

mind the information given so far, they should have some idea as to 
the melting of the article, to the mixing and the forming of the 
molten mass before solidification, and to the use of the blowpipe. 
They should be able to grasp the principle of the execution of welds ; 
but more practice and more study are necessary to make proficient 
welders. 

Homogeneous welding is the union of bodies by fusion. Dsually 
the operator does not melt enough, does not get the edges molten 
before he lets the molten rod fall on the unwelded surface. Or he 
makes holes, and tries to fill them up by adding the feeding-rod, 
which usually drops on the cold surfaces. But by quiet determined 
tuition and practice the student soon comes to know what are 
the defects and makes great effort to remedy them. He must prac- 
tise every form of welding, but must first of all master the commonest 
joints, such as the butt and the edge. These joints must be done 
over and over again before he is allowed to proceed with further 
kinds of welds. This is imperative if he intends to become a first- 
class operator. Two joints should be made : first, weld with welding- 
rod ; second, without welding -rod ; third, with welding -rod, hammer, 
and anneal. 

The two tests should be butt and edge, and ^-inch thick steel. 
"Bending test" may be made by fixing in the vice the article 
welded with the line of the weld just | inch above the vice, then 
bend right over with a hammer. "Area test " : Two pieces put at 
right angles, and weld along the corner, seam, then flatten out with 
hammer ; see if the area is the same thickness as the material welded. 
Third test: Two pieces ^ inch thick; butt and weld; use plenty of 
welding-rod. After welding, heat the piece up to white heat by 
blowpipe, hammer to thickness of metal ; repeat the heating by the 
blowpipe, and allow to cool; and then bend in the vice. Watch 
the difference between the annealed one and the one not annealed. 
If these tests fracture when bent, repeat the welding and testing of 
these two articles until they can be done without cracking or fracture. 

Operators in the first few courses of training generally point the 
flame on to one of the faces of the bevel. As the metal melts it 
runs down on the other " cold " side. It is usually covered over 
by the molten metal, and is not seen externally; but the defect is 
there, nevertheless. Operators must not allow this to occur, but 
must remember that the simultaneous and regular melting of the 
two edges of the weld and the welding-rod is a very important point. 
If good welds are to be obtained, this is a sine qua non. The begin- 
ning of the weld is always slower, and the end more rapid, because the 



METHODS OF WELDING 



87 



temperature of the article is increased as the line of welding reaches 
the end. The finishing must be done sharply, otherwise the metal 
gets so molten that the ends give way and allow the molten metal 
to run away. 

We may now proceed to autogenous problems. The vast amount 
of welding carried through during the war was really amazing. The 
thousands engaged on this process were chiefly concerned with 
mild steel articles for military purposes. Millions of feet of sheet 




Fig. 33.— Round Bar Bevel, Chisel Points. 

steel were welded, and the task of training these temporary operators 
was huge. Of course, there was no time to impart a thorough know- 
ledge of welding. They were given just sufficient instruction to enable 
them to get along and practise for themselves. It was remarkable, 
however, how quickly they settled down to the plain welding of mild 
steel articles. These welds apparently are the most easy to obtain, 
but in reality, to do them as they ought to be done, so that they will 




M 



Fig. 34. — Tube Bevel. 



stand any test applied, is not so easy. Indeed, they require on 
the part of the operator the utmost thought and care. It is 
well known that 90 per cent, of welding is in mild steel, therefore 
the operator will have to be taught the constituents and analysis 
of these metals. He must also make himself acquainted with the 
melting-points of the metals and their oxides. He must study the 
articles on the different metals in other parts of this book, and must 
especially learn to know the melting-points of all metals and their 
oxides. This is most important in the cases where the metals and 
their oxides differ in their melting-points. Take, for instance, steel 



88 



MODERN METHODS OF WELDING 



and aluminium. Steel is 1,600° C, aluminium 700°' C. In the case 
of the oxides the difference is very much greater. Aluminium melts 
at 700° C, but its oxide melts at 1,600° C. ; this is why operators 
do not find aluminium welding easy of execution. The metal itself 
readily forms in globules or beads, which do not run together 
owing to the outside film not being melted. These films are the 
oxide. The same happens to all metals, but others are not so much 
defined as aluminium. 

There are many defects that happen in welding which could be 
avoided if operators would see if they were corrected as they went 
along. Some of the defects in welding mild steel will be described 
below. 

The first is the lack of penetration — that is, either the power of 
the blowpipe has not been large enough or the operator has passed 





Fig. 35. — Fracture after Bending. Fig. 36. — Lack oe Penetration. 



over the line of welding far too fast. This lack of penetration is a 
serious defect, and is a defect that is commoner than any other, 
especially in the case of butt welding. By not penetrating right 
through the metal, the original thickness of the metal is reduced 
in sectional area, because the weld has only penetrated to two-thirds 
of its thickness. This is very serious, and in the case of tubing which 
has to stand pressure very often the weld gives before the full 
pressure is put on. This non-penetration occurs sometimes when 
the edges are not bevelled. The heat has not been sufficient for 
the fusion to go right through the whole thickness of the joint, 
and also the thickness not welded constitutes a starting-point for 
a break. 

Figs. 35 and 36 show the weld, and the result of the bending. 

On the other hand, operators should take care not to penetrate 
too far through, or the metal runs through from the molten bath 
above, and often leaves a conical hole which is difficult to fill up and, 
in doing so, generally oxidises the metal owing to being too long on 
the weld, and the metal is burnt. 



METHODS OF WELDING 



Adhesion is another defect which operators often make, especi- 
ally in thick bevelled work, owing either to not having a powerful 
enough blowpipe or to too heavy a pressure of oxygen, which 
" swills " the surface of the bevel, without taking time to make it 
liquid; dropping the liquid rod on this "swilled" surface causes 
it to stick or adhere. This is not fusion. Then, again, some opera- 
tors do not melt both edges together, and therefore, again, no fusion 
or unity takes place. Again, many welds are interposed with oxide. 
This arises from several causes. The metal may not have been 
properly liquefied, which causes blowholes to form in the interior 
of the molten mass and remain after solidification. Likewise, if the 
metal gets too hot and boils, this causes gas to be imprisoned in the 
interior of the weld, also producing blow-holes. The defect may 
also arise from not attacking the bevelled edges of the weld suffi- 





Fig. 37. — Single Bevelled Joint. 



Fig. 38. — Adhesion, Bad Weld. 



ciently, or attacking them unequally, or from the flowing of the 
metal or the liquid welding-rod on the edges that have not been 
melted. 

Operators must pay attention to this point and understand that 
the molten metal flowing from the edge of the weld brings about 
adhesion if this part itself is not melted. It is very important 
indeed that, before the bevelled edges are melted, the bottom of the 
bevel should be melted first, so that as the sides of the bevel are 
melting, the liquid metal runs into the molten bath lying ready to 
receive it at the bottom of the bevel. If this is carried out there 
will be no adhesion. 

It is important that all welds, no matter for what job, should 
always be well filled. There must be no part of the weld, on either 
side, under the full section of the metal which is being welded. 
If it is, the article loses its strength. This is almost as much to be 
avoided as a bad weld. Assume a tube is being welded j inch thick. 
A butt joint is being made, and it is welded along the line of the 



90 



MODERN METHODS OF WELDING 



weld with what is, from the operator's point of view, a good weld. 
It is inspected and found to have, in two or three places along the 
outside lines, indents about ^V inch deep. These indents were caused 
by the melting of the original metal, which flowed with the circular 
movement of the blowpipe, and left the indents behind. These 
should have been filled up with the welding-rod as the welding pro- 
ceeded. Consequently, through this error, the tubing will not stand 
the full amount of test designed for J inch thick. The finished 
sectional area is only -$■% inch thick. If ^ would do, why use \ inch 
thick ? Operators, however, must learn to keep the welds up to 
the thickness of articles. These articles are skilfully designed and 
the stresses all calculated out for the purposes to which they 
are to be put; therefore, if the welding all over is not up to that 



First Start 
oP Fracture 






Fig. 39. — Not Fully Penetrated, 
First Starting of Fracture. 



Fig. 40. — Not Penetrated Through. 



particular thickness the article is not so strong. In some cases 
this is important. 

Tests for Welds. — The majority of defects are hidden in the body 
of the weld, and the operator is often ignorant of them. But there 
are many ways of testing welds, so that after he finds them out 
he should be able to overcome all his defects. This will take some 
time, but with patience and close study he should be successful. 
One cannot, of course, break joints of commercial work in order to 
get stresses and strains or examine the internal constitution. But 
with facilities to make his own test-pieces of similar metal to those 
he has worked with, the operator is able to make all the tests neces- 
sary, including resistance and elongation. Test by corrosion, or, 
as it is called, the micrographic test, may be applied to all metals 
of yV mcn or over. 

Two pieces of flat bar should be welded, about 3 inches long, 
butt- jointed, and then cut through the longitudinal way, across the 
weld. One of the faces is to be polished to a spotless surface, all 



METHODS OF WELDING 



91 



grease is removed, and the etching fluid, applied with a brush, 
soon exposes any defect, adhesion, or oxide. A plain black image 
appears which shows all flaws very plainly, and if it has been burnt 
this also can be clearly seen. It is important that the face be polished 
well and free from grease. The polishing does not disclose any 
defect, unless it be a bad one ; but when the etching fluid is applied, 
the defects appear instantly. Therefore, if operators will from time 
to time practise these tests, they will soon remedy the defects. 




Fig. 41. — Bending a Test-Piece in a Vice. 



Etching liquid may be as follows : 

Iron and steel 

[water . . . . 10 parts. 

Iodine solution^ potassium iodine 2 ,, 

[iodine . . . . 1 part. 

The solution is applied with a brush immediately the polished 
cut is ready. The structure develops almost suddenly, and in a 
few minutes the corrosion is sufficient. Wash with running water, 
dry with alcohol, and cover with a layer of varnish if the test is to 
be preserved. The test by bending is one applied in most technical 
schools, and is appropriate for all ductile metals. A test-piece may 
be made out of f-inch diameter round steel. This must be first 
prepared for welding by shaping two ends to chisel type ends. 
The reason why it must be pointed as a chisel is that, as the metal 
is welded, it falls down to the bottom where the chisel-point meets, 
at the centre of the round bar. If it were not for the chisel-point, the 



92 MODERN METHODS OF WELDING 

article being round, the metal would run to the bottom of the 
welding table and spread about instead of building up. The welding 
of this round piece should be executed and finished off the same 
thickness as the bar itself, so as to give it a fair test when bending; 
after welding and cooling it can be put in the vice, with the weld 
just over the top of the jaws, the hammer applied in any direction. 
It should be bent over to a radius of 1J inches. If this is done 
without a crack or fracture, the work will pass. 

The hammering and annealing test is the best of all. Operators 
should weld several of these small test-pieces in various sections of 
steel. One-third of the test-pieces to be put through the three 
tests of corrosion — bending, hammering, and annealing — should be 
pieces where welding only has been done ; one-third should be pieces 
which have been welded, annealed, and- hammered; annealed and 
cooled slowly. A record of all these tests should be kept, and the 
result will be surprising. The illustration (Fig. 41) shows a test- 
piece in a vice; this is a very easy method of the bending test; 
students who can execute welds to stand this test should be able to 
tackle all ordinary commercial work. 



CHAPTER XVII 
PREPARATION OF WELDS 

It is impossible to overestimate the importance of thorough pre- 
paration of the work before the weld is actually attempted. Any 
time spent in this way is amply repaid afterwards in the easier 
execution thus made possible. The preparation varies considerably 
with the nature of the metal and the thickness and form and posi- 
tion of the parts or articles to be welded. It is impossible to lay 
down any hard-and-fast rules. For each metal we may have to 
adopt a different preparatory procedure. For instance, some of 
the metals have much lower melting-points than others, and must 
be dealt with accordingly. 

The general principles obtaining in the best practice direct 
that the line of weld must be opened out — -that is, the two sides 
bevelled, each to 45 degrees, making an angle of 90 degrees. This 
is to make certain that the weld shall be penetrated, and not merely 
sealed over. The welding must be done from the bottom of the 
bevel and properly filled in with the welding-rod, the metal at the 
edges being molten at the same time, so as to unite with the molten 
rod; the two combining make a good sound weld. Bevelling also 
increases the area of the surface of the weld, thereby strengthening 
the latter. It allows the addition of a larger quantity of metal of 
better quality, since rods of pure iron are added to the welds. 
Bevelling is carried out on thicknesses of £ inch. After it 
reaches \ inch and over in thickness, the bevel should be on both 
sides. The illustrations on p 94 show two pieces. 

It is essential that the line of welding should be thoroughly 
cleaned (particularly in the case of aluminium), either by hand 
tools or by some chemical agent. Too much stress cannot be put 
on this, as welders often find. The most important part of the pre- 
paration is that of arranging the pieces to be welded in such a posi- 
tion that there will be no deformation, fractures, cracks, or internal 
strains, and that they will be linable at the conclusion of the opera- 
tion. This applies chiefly to cast-iron articles, which are generally 

93 



94 MODERN METHODS OF WELDING 

intricate castings of various thicknesses and irregular shapes and 
are often cumbersome. 

This is a point in which the skill of the operator is revealed, 
as there are no fixed rules to guide him. Welders too often fail 
to take sufficient precautions to keep the article adjusted and in a 
correct position for welding, so as to allow for that phenomenon 
known as expansion and contraction, and to leave the welded article 
finable at the finish. One must keep in mind that old maxim: 




Flat Bab Double Bevel. 



" What is worth doing is worth doing well." A weld well prepared 
is half done. As the result in welding depends to a certain degree 
on how the preparation has been carried out, one cannot spend too 
much on it, especially where intricate, uneven castings are concerned. 
It is the interested, careful, and thoughtful workman who gets success 
in the welding of such articles. 

Bevelling should be done on both sides, as has been said, if over 




Fig. 43. — Angle Iron, Bevelled One Side. 

\ inch thick. If it cannot be got from both sides, then a deeper 
bevel must be made on the one side. Operators sometimes do not 
bother about bevelling, even if it is a case of \ inch thick without 
bevelling. To omit it always leads to bad results — such as bad 
penetration, adhesion, or overheating of the metal — and usually 
leaves about \ inch unwelded at the bottom edge. This reduces 
the sestional area, and is the means of starting a fracture (see 
the illustrations below), which is what happens when the articles 
are not welded through. If the above defective weld were tested, 
it would hardly stand a tensile test of three-fifths of the original 



PREPARATION OF WELDS 



95 



strength of the metal. Taking a good view of the above section, 
one sees that the weld does not touch the bottom joint of the bar. 
Further, it can be clearly observed that the molten metal did not 
penetrate through the full thickness, but formed itself into a semi- 
circular mass at the bottom joint of the bar. This semicircular 
line reduces very much the area of the weld, and with it the strength. 
If a proper weld had been made, a f-inch plate would have been quite 




Fig. 44. — Not Penetrated. 

as strong, and a great saving of material in the thickness of the 
respective plates would have been effected. In the illustrations the 
lines marked A and B show the thickness of the metal not welded. 
This is a great consideration from an engineer's point of view. He 
designs work calculated, on a specified thickness, to stand certain 
stresses; and it may, in any particular instance, be a very important 




Fig. 45.- 



-Sface between A and B shows Amount Unwelded, and Fracture 
when Bent. 



job, where the stresses must be kept up to counteract the design. 
But if a bad weld is made and does not penetrate to the thickness, 
then the article will fail, and cause heavy loss. On the other hand, 
if one was sure of always penetrating the weld (which can only be 
done by preparing and bevelling), articles can be designed with 
lighter materials, thus saving expense. 

The above sketches show very clearly how defects occur; the 
welding has not been penetrated through the whole thickness. 



96 



MODERN METHODS OF WELDING 



hence the strength is not up to the thickness of the original metal. 
Upon bending the bar, the unweldecl line opened, and also started a 
fracture along the line of welding. 

One cannot be too emphatic in stating that pure metals, pure 
welding-rods, pure gases, are most essential to good welds. Adjust- 
ment before welding is a point in which the experience and skill of 
the operator tells. There are very few rules for his guidance, as 
the articles are so different that each one has its own particular 
scheme. Upon any work but that of the simplest character, failure 
to grasp and apply the laws of expansion means partial or total rum 
of the work. It is impossible to control expansion and contraction 




Fig. 46.- 



-Machine Operator Welding Seams 116 Inches Long in Corrugated 
Sheets for Transformers. 



by physical or mechanical forces. The only way to prevent disastrous 
results is to foresee the probable direction and extent of the pheno- 
mena and nullify the effect by preheating the whole or certain parts 
of the work, either by the blowpipe or the welder's furnace, the latter 
being recommended. 

Operators must take precautions with all articles of non-ductile 
matals, to see that they are all properly adjusted, and carefully 
fixed at some part of them, to prevent them being moved or dis- 
turbed during the process of welding. They must provide that ex- 
pansion and contraction shall take place uniformly, so that the 



PREPARATION OF WELDS 



97 



article is not, after welding, distorted in any way nor out of 
alinement. There are various ways of making these fixtures, and 
a series of different sizes should be kept. One is illustrated below, 
which is easily manipulated, even when hot from the furnace. 

Expansion in physics is an enlargement or increase in the bulk 
of bodies, in consequence of a change of their temperature. This 
is one of the most general effects of heat, being common to all bodies 
whatsoever,, whether solid or fluid. The expansion of solid bodies 
is determined by the pyrometer. One can realise the force of expan- 
sion from water that has frozen in an enclosed vessel or pipe. When 
the careless motorist leaves the cooling water of the engine in the 
water-jacket of the cylinder overnight, on a frosty day, the next 




Fig. 47. — Casting Broken. 
Left: Bevelled and cramped setting for welding. Right: Welding completed. 

morning there may be ice. On which heating by water or other- 
wise, the ice expanded, and this powerful force fractures the cylinder 
water-jacket owing to there being no outlet for the expansion. 

This same phenomenon is seen with all cast-iron articles. It 
is useless to attempt by force to oppose this expansion and contrac- 
tion. The method is to avoid or limit the consequences. If not, 
any welding done on non-ductile articles will surely cause deforma- 
tion, cracks, and internal strains. The whole articles should be raised 
to a temperature, in the case of cast iron, of not less than 900° C. 
and not exceeding 1,100° C, and then quickly welded, and returned 
to the annealing furnace to cool slowly. 

It must be understood that there is no other means of obtaining 
good results on non-ductile articles, except that of preheating and 
annealing on properly designed and well-thought-out lines. In cases 



98 



MODERN METHODS OF WELDING 



45" Bevel 



~=§*& 



Finished weld. 

= jFT -i 



g j 



/ r /^. 4$. Proper set up for butt 
welding of pipe, and finished 
weld. 



Bevel here 




Section showing 
finished weld. / 




Fig. 49- Welded cross in pipe, left , 
bevel right, welded. 



Bevel here 
\ 



Section showing 
finished weld. 



F>9- 



\/=== 




50. Showing construction of 



T pipe, bevel and weld 
Bevel here. 




Section showing 
finished weld 




Fig. 51. Showing pipe at 45 degrees, 
weld and bevel. 



Figs. 48 to 51. 



PREPARATION OF WELDS 99 

where the articles are free to expand and contract and are fairly even 
in thickness and size, welding may be done without preheating. 
These articles will not crack when welding; but they are few, and 
should be carefully watched. After welding they should be placed 
in the annealing oven to remove all internal strains, and left to cool 
slowly. 

The illustration on p. 97 is a case where it is not necessary to 
take expansion into consideration, as there are no tied ends. The 
casting may therefore be welded from the cold state ; but, from an 
economical point of view, it should be heated to save the gas. The 
illustration referred to shows how a casting should be prepared for 
welding. The line of bevelling can be seen; the under side is 
similarly bevelled ; the fixing of the cramps will be noted, holding 
the casting in position while the welding is performed. 

In making the set-up for butt-welding pipes the edges should be 
separated sufficiently to allow the heat of the welding flame to drive 
all the way to the bottom of the weld. This separation, however, 
should not exceed ^ inch, because too great separation is conducive 
to the formation of large bumps of metal within the pipes, which is 
very undesirable. Many operators butt the edges of the pipe 
" square up " and do not attempt to secure complete penetration. 
The weld is slightly reinforced and is virtually as strong as any portion 
of the pipe. The edges of the butt weld in the pipe and, more par- 
ticularly, those of other fittings shown herewith should be bevelled 
Simple as these lay-outs appear, the average operator experiences 
more or less difficulty in getting the various parts to line up satis- 
factorily. 

Figs. 48 to 51 show several tube joints, described above. 



CHAPTER XVIII 
WELDING TABLES 

Small welding tables are used in both small and large workshops. 
There is quite a variety of types, from which one may select any 
particular one. They are built so as to give an easy position to the 
operator, who can work all round it. 

This facilitates the task very much, and the weld is done quicker 
and better. The tables are portable and can be moved anywhere. 





Fig. 52. — Mild Steel Operator's Table. 




They are usually constructed of angle-iron formation, and all the 
joints are welded. They may be light, and 1J by ■§• angle steel is 
strong enough for all ordinary purposes. The making is quite 
simple, being a matter of a few hours for any intelligent operator. 
Firstly, there are two frames, say, 2' 9" X 1' 9", which can be 
made in one piece; cut a V out of each corner; then bend at those 
places where cut out and weld up. Then the four legs should be 
welded to the frames, the one of which is on the top of, and the other 
inside, the legs, 8 inches from the bottom. This bottom frame should 

100 



WELDING TABLES 101 

be fitted with a mild steel plate, dropped closely into the angle frame, 
forming a tool table, where the operator can keep his tools and weld- 
ing-rods. Tables are usually made 2 feet 3 inches high, but this may 
be altered to any height. 

The following are illustrations of ordinary types, but they may 
be varied to suit circumstances. 

One of them is shown plain and one with fire-bricks. Notice 
strips welded across the top frame to carry the bricks; the other is 
shown with fire-bricks in position. It is very necessary for fire- 
bricks to be put under articles to be welded, because the brick retains 




Fig. 53. — Adjustable Welding Table, with Vice Attached. 

the heat, which assists the heating of the articles being welded, 
thereby saving gas. This is much better than having a bare steel- 
plate table, which often warps by the continual heating. The size 
of the top may be determined by the layer of bricks, and these should 
be laid out before the frame of the table is made, so as to get the 
correct size for the bricks to fit well together. 

Fig. 53 is an adjustable type and can be turned at any angle. 
This is found exceptionally useful on repairs, when the welding 
is not horizontal. One has a vice attachment, and is very useful. 

In large shops, where there are a large number of operators on 
repetition work, it is a practice to construct long tables at which 
thirty to forty operators can all work. They usually work face to 



102 MODERN METHODS OF WELDING 







e i' 1 " a 'i.< 



Fig. 54. — Welding Table with Fire-Bricks. 




Main from Generator 



^ 



U 



^ 



^ 




Fig. 55. — Table for a Number of Operators. 



WELDING TABLES 



103 



face — that is, in pairs each side of the table. The acetylene main 
gas pipe is usually brought over the centre of the table, and the 
hydraulic safety valves are suspended from the main supply to a 
convenient position for the operators. They are spaced according 
to the requirements of the articles being welded without crowding. 




Fig. 56. — Tilting Table. 
Articles can be bolted on. 



In construction, these tables are almost identical with the smaller 
ones, with the exception that no frames are used, except the framing 
under the boiler-plate top. Such large tables usually have large 
flat bricks, about 1J inches thick. Fig. 55 is a sketch of one, 
showing the position of the acetylene main gas-supply, from which 
are suspended the hydraulic safety valves, one for each operator. 
The tables may be extended to any length, to the limit of the shop 
and the supply of acetylene. 



CHAPTER XIX 
FURNACES FOR HEATING 

In the repair of non-ductiles, it is necessary to heat them up before 
the welding can take place. It is impossible to make satisfactory 
welds of cast-iron or aluminium articles without first preheating to 
a level temperature. If an attempt is made to weld any articles of 
the metals stated above, without getting hot all over, fractures take 
place. For instance, take a casting of iron just as it is, without 
preheating. Apply the blowpipe at any place, get a good heat, 
and the result is that you will hear it crack in some part other than 
where heated. When the casting gets cold again, further fractures 
are sure to occur. These are caused by the uneven heating of the 




Fig. 57. — Kerosene Preheating Torch. 

article in one place with the blowpipe, causing the non-conducting 
metal to expand where it was hot, while the cold part of the casting 
remained normal. 

The methods adopted to overcome this expansion and contrac- 
tion on non-ductile articles are very simple, if care is taken to pro- 
vide the right appliances. One is to use a furnace with coal, coke, 
charcoal, or gas. Coal would be all right in a properly constructed 
furnace, where the flame is reverberatory, and a second floor has 
been made for the heating of the articles which are not in actual 
contact with the fire. But the author's experience is that this 
method is much too costly to maintain. The expense would be 

104 



FURNACES FOR HEATING 



105 



prohibitive in a small shop, unless there was a good quantity of 
castings to weld daily. Also the heat is too fierce, and would not 
do at all for aluminium, which would probably collapse before 
it could be got out. The coal furnace should only be used in large 
shops. Although there are many of these furnaces being used, 
with coal, coke, and charcoal, and, to a certain degree, giving 




d5=d«^^£ 



Fig. 58. — Gas-Heated Preheating Oven. 



satisfaction, they are generally employed in conjunction with other 
work. The best method, with the least initial outlay, the most 
economical working, and the best even heating, is a furnace heated 
by gas at either ordinary or high pressure. Fig. 58 shoAvs an 
excellent type, which gives exceptionally good results; it is not 
hard to make, and it will not be expensive. 

Fig. 57 shows a preheating kerosene torch. This is ideal for 



106 



MODERN METHODS OF WELDING 



the repair shop; it is light, portable, and owing to a patented 
sliding valve, can be operated in any position. It produces a 
clean even flame of about 3,000° F. and 24 inches long. It con- 
sumes about 1 gallon of kerosene per hour. The tank capacity 
is 3 gallons. The burner thoroughly vaporises the kerosene, and 
the flame cannot blow out in the wind. It is very good for pre- 
heating work and also for annealing. The weight is 25 pounds. 

The preheating oven or furnace shown on p. 105 is easy to con- 
struct from sheet steel. It was designed by the author, and has 
proved very efficient in use. It may be made any size to suit the 
work in hand. The one illustrated is 4 feet deep, 3i feet wide, 3 feet 
long. The construction consists of an inner and outer casing, with 




M 



u^ 



Fig. 59. — Folding Asbestos Screen, eoe Preheating Furnace. 



1J inches space between them, filled with asbestos. The back of 
the stove (inner and outer) must have the asbestos put between 
before bolting up the stove. There is an outlet at the back, near 
the top, to allow the burnt gases to escape, and the piping should be 
carried from the outlet to the atmosphere. On the inside of the 
stove are bearers or ledges for perforated trays, in which trays the 
articles for heating are fixed. The door is also made of two sheets 
of steel, with asbestos between them, and fits very closely to prevent 
any cold air from getting into the interior. Along the bottom are 
four Bunsen burners. These may be purchased from any reliable 
firm, but they must be the best that can be got. 

A great saving in gas can be made by adopting, for the purpose 
of extracting all the heat from gas, a folding asbestos cover as in 
Fig. 59. It is made like a fourfold screen. After the article to be 



FURNACES FOR HEATING 



107 



heated is put in the stove, and before the gases are lit, it is placed 
on the top of the article. When the gases are lit, this cover concen- 
trates the whole of the heat, thereby getting the article heated in a 
much shorter time, and saving quite 50 per cent, of the gas. This 
asbestos cover can be used for preheating and also for annealing. 
The screen described may be made in smaller or larger sizes to suit 
the work required. The perforated tray in the furnace is made to 
draw out with the article on it. 

The handling of castings, such as a four-cylinder motor casting, 
when hot, is a very troublesome job if there are no proper appliances. 
Hence, fractures often occur through not getting the articles quickry 
enough into the annealing furnace, and allowing the temperature 
to fall into the expansion zone — that is, 850° C. The author has 




Fig. 60. — Light Lifting Crane for Use in Lifting Castings In and Out 
of the Preheating Furnace. 



known this to occur on many occasions. Good welds have been 
executed, but they have been left one or two minutes too long before 
getting them into the annealing furnace, and very often the fracture 
is much larger than the original fracture. An appliance which will 
be found to overcome this difficulty of removing and inserting the 
hot articles rapidly, with ease and comfort, is shown in Fig. 60. 
This should be installed in all workshops where they are dealing 
with heavy repairs, which have to be preheated. It is simply a 
small swinging overhead crane, very lightly built, to carry about 
5 cwt. It has two small wheels, running along a flat bar on edge. 
Suspended from the plates of the wheels is a lever about 9 feet 
long, a hook on the end, and a rope at the other. 

The rope is for lifting the weight suspended at the other end ; on 
the hook may be hung a two- or four-legged chain to lift the articles 



108 MODERN METHODS OF WELDING 

already fixed on the oven tray. The hot casting may thus be put 
in and out of the oven or furnace with ease, and without any of the 
welders getting burnt. 

The phenomenon of expansion and contraction with reference 
to metals is one of the most important problems in the welding pro- 
cesses. No operator can become competent without devoting long 
study to it. Cast iron is a non-ductile metal — that is, it can only 
expand and contract in its whole piece. Hence, if heat is applied to 
one part of the article, the heated part becomes expanded past its 
elastic limit. The cold part of the article does not expand and the 
heated part is therefore fractured. On the other hand, if the whole 
article had been heated, by putting in a- proper heating furnace, 
and the heat carefully regulated until it had reached a minimum of 
900° C, the article could have then been taken from the furnace and 
put on the welding table, welded, and put back into the annealing 
furnace and allowed to cool slowly, preventing any cold air from 
getting near it, when the article would be quite sound without 
crack or fracture. 

This operation of expansion and contraction is so important, and 
the methods to counteract it are so easy, sure, and effective, 
that, in all cases where welding of non-ductile articles is done, one 
must see to it that these operations of preheating and annealing are 
carried out. 



CHAPTER XX 
IRON AND STEEL 

The mechanical properties of metals are often, in a great measure, 
dependent on the thermal treatment to which they have been sub- 
jected. There can be no question that the application of heat to a 
metal may produce a remarkable molecular change in its structure, 
the nature of the change depending on that of the metal, and on the 
treatment it has undergone. It will be well, therefore, to consider 
carefully what happens when the metals are submitted to three 
principal operations involving thermal treatment, which are known 
respectively as annealing, hardening, and tempering. Usually all 
three are intimately related. Annealing may be defined as the 
release of the strain in metals, which may itself have been produced 
by mechanical treatment, such as hammering, rolling, or wire- 
drawing, or by either rapid or slow cooling from a more or less 
elevated temperature. 

As an example of the former, it may be mentioned that metals and 
alloys which have been rendered excessively hard by rolling are 
heated usually to bright redness and allowed to cool slowly. In the 
case of copper it does not appear to be important whether the cooling 
is slow or rapid, and in recent years much experimental evidence 
has been accumulated which tends to show that, in the case of certain 
metals which have been hardened, a more or less prolonged exposure 
to a low temperature under 100° C. will sensibly anneal them. 
On the other hand, the rapidity with which cooling is effected is very 
important. Bronze containing about 20 per cent, of tin is rendered 
very malleable by rapid cooling. In the case of iron and steel the 
thermal treatment is especially important. 

Steel, it must be remembered, is modified iron. The name iron 
is, in fact, a comprehensive one, for the mechanical behaviour of 
the metal is so singularly changed by influences acting from within 
and without its mass as to lead many to think that iron and steel 
must be two distinct metals: their properties are so different. 
Pure iron may be prepared in a form as pliable and soft as copper 
— -for instance, the charcoal used for welding. Steel can readily be 
made sufficiently hard to scratch glass. Notwithstanding this extra - 

109 



110 MODERN METHODS OF WELDING 

ordinary variation in the physical properties of iron and certain kinds 
of steel, the chemical difference between them is small, and would 
hardly secure attention if it were not for the importance of the 
results to which it gives rise. 

It is necessary to consider the nature of the transformations 
which iron can sustain, and to see how it differs from steel. Its most 
useful and advantageous property is that of becoming extremely 
hard when ignited and plunged in cold water, the hardness produced 
being greater in proportion as the steel is hotter and the water colder. 
The colours which appear on the surface of steel slowly heated 
direct the artist in tempering or reducing the hardness of steel to 
any determinate standard. 

Hardening is the result of rapidly cooling a strongly heated mass 
of steel. 

Tempering consists of reheating the hardened steel to a tempera- 
ture far short of that to which it was raised before hardened. This 
heating may or may not be followed by rapid cooling. 

Annealing, as applied to steel, consists in heating the mass to a 
temperature higher than that used for tempering, and allowing it to 
cool slowly. 

This may be seen experimentally in the following manner : Three 
strips of steel of identical quality may be taken. It can be shown 
by bending one that it is soft, but if it is heated to redness and 
plunged in cold water it will become hard and will break on any 
attempt to bend it. The second strip may, after heating and rapid 
cooling, be again heated to about the melting-point of lead, when it 
will bend readily, and will spring back to a straight line when the 
bending force is removed. The third piece may be softened by being 
cooled slowly from a bright-red heat. This will bend easily and 
will remain distorted. 

The metal has been singularly altered in its properties by com- 
paratively simple treatment. And all these changes, it must be 
remembered, have been produced in a solid metal, to which nothing 
has been added, and from which no material has been taken away. 
The theory of the operation described above has been laboriously 
built up ; its consideration introduces many questions of great interest 
both in the history of science and our knowledge of molecular physics. 

Physical Properties of Metals. 

Molecular Structure. — The physical aspects of metal are so pro- 
nounced as to render it difficult to abandon the old view that metals 
are sharply defined from other elements, and form a class by them- 



IRON AND STEEL 111 

selves. Like all other elements, metals are composed of atoms 
grouped in molecules. Any force that alters the relations of the 
atoms in molecules modifies the physical properties of the metals. 
Indeed, it would be easy to show that the physical constants of each 
metal vary with its degree of purity. The molecular grouping of 
metals is doubtless very varied, and little definite is known 
regarding the structural stability of most of them; but it may be 
assumed that it is not very great, as some metals split up into single 
atoms when they are volatilised, and most of them unite readily 
with chlorine and oxygen. Consequently, any mass of which the 
fundamental molecules are the constituent particles may practically 
be regarded as a single molecule. Two fundamental molecules must, 
however, be held to be capable of uniting to form complexes that 
have less power of cohering, and any circumstances tending to bring 
about the formation of such complexes would tend to make the 
material less tough. This may account for the extraordinary altera- 
tion in the properties of many metals produced by very small quan- 
tities of incompatible foreign matters. 

Density. — The density of the metal is dependent on the intimacy 
of the contact between the molecules. It is dependent, therefore, 
on the crystalline structure, and is influenced by the temperature 
of the casting, by the rate of cooling, by mechanical treatment, by 
the purity of the metal. All metals, except bismuth, are lighter 
when molten than in the solid state. In the case of cast iron, which 
passes through a pasty state on solidification, the density is aug- 
mented by wire-drawing, hammering, and any other physical method 
of treatment in which a compressing stress is employed. Mere 
traction, however, may diminish the density by tending to develop 
cavities in the metal. Pressure on all sides of a piece of metal 
increases its density. A metal can only be compressed if the 
result of the application of pressure is to cause it to pass to an 
allotropic state — that is, denser than that which it originally 
possessed. 

Fracture. — The appearance of the fractured surface of a metal 
depends partly on the nature of the metal and partly on the manner 
in which solidification occurred. Sudden cooling, to a great extent, 
prevents the formation of crystals, while slow cooling facilitates 
their development. Long, continual hammering, frequent vibra- 
tions, and intense cold will produce the latter result. Any condition 
that affects either the cohesion or the crystalline structure of a metal 
affects its fracture. 

Malleability. — This is a property of permanently extending in 



112 MODERN METHODS OP WELDING 

all directions, without rupture, through pressure produced by slow 
stress or by impact. As a rule, crystalline metals are not malleable, 
and any circumstances that tend to produce crystallisation must 
affect the malleability. Thus, in nearly all metals, the malleability 
becomes impaired when they are subjected to rolling or long- con- 
tinued hammering. But this property may be regained by anneal- 
ing, which consists in raising the metal to a high temperature and 
allowing to cool, either rapidly or slowly. At different temperatures 
metals behave in different ways. 

Every malleable compound of iron, containing the ordinary 
elements of that metal, which is obtained either by the union of pasty 
masses of the iron or by any process involving fusion, and which 
cannot be hardened by an ordinary method, will be called by us 
" wrought iron." 

Ductility is the property which enables metals to be drawn into 
wire. It generally decreases with an increase in temperature of 
the wire at the time of drawing ; but there is no regular ratio between 
the two. Iron is less ductile at 100° C. and more ductile at 200° C. 
than it is at 0° C. 

Tenacity is the property possessed by metals, in varying degrees, 
of resisting the separation of their molecules by the action of a tensile 
stress. 

Toughness is the property of resisting the separation of the mole- 
cules after the limit of elasticity has been passed. 

Hardness is the resistance offered by the molecules of a substance 
to their separation by the penetrating action of another substance. 
Great differences are observable between the hardness of various 
metals. 

Elasticity is the power a body possesses of resuming its original 
form after the removal of an external force which has produced a 
change in that form. The point at which the elasticity and the 
applied stress exactly counterbalance each other is termed the 
" limit of elasticity." If the applied stress were then removed, the 
material acted upon would resume its original form. If, however, 
the stress were increased the change in form would become per- 
manent, and permanent set would be effected. Within the limit 
of elasticity, a uniform rod of metal lengthens or shortens equally 
under equal additions of stress. If this were the case beyond that 
limit it is obvious that this would stretch the bar to twice its original 
length, or shorten it to zero. This stress, expressed in pounds or 
tons for a bar of 1-inch square cross-section, is termed the modulus 
of elasticity. 



IRON AND STEEL 113 

The ultimate tensile strength or maximum stress the material 
can sustain without rupture, the limit of elasticity, and the breaking 
stress are the points which usually have to be determined, and these 
alone will be considered here. In testing a piece of metal, the first 
point to be determined is the limit of elasticity. When a metal, 
such as a piece of iron or steel, is submitted to stress by pulling its 
ends in opposite directions, it stretches uniformly throughout its 
length. There is, however, in such a solid a limit in the applica- 
tion of the stress up to which the metal, if released, will return to 
its normal length. This point is the limit of elasticity. 

Influence of Foreign Elements on the Strength of Metals. — The 
influence of chemical compositions on the mechanical properties 
of metals is of great importance. The influence of foreign elements 
is best shown in the case of iron. The properties of this metal are 
absolutely changed by the presence of a few tenths per cent, of 
carbon. Phosphorus and silicon produce very dangerous impurities 
in iron. It is difficult to estimate the influence of silicon. It is 
known that its addition to molten steel is useful, as it prevents the 
formation of blowholes in the solidifying mass. 

The colour of metals is influenced by their purity. Thus, iron 
becomes white by the admixture of carbon, silicon, sulphur, and 
phosphorus. All metals are fusible. When strongly heated, they 
pass from a brownish-red to a clear red colour, which gradually 
increases in luminosity and transparency to a dazzling white. On 
solidifying from a molten state, metals frequently exhibit efferves- 
cences due to the expulsion of absorbed gases. This expulsion, before 
solidification, causes a sudden outburst of metal through the surface. 
When it passes from the liquid to the solid state, it either does so 
suddenly, or it passes through an intermediate pasty stage. This 
fact is occasionally of great metallurgical importance. 

On solidification after melting, metals usually crystallise. 
The crystallisation of metals is of great importance, as the formation 
of crystals, due to continued vibration, intense cold, sudden altera- 
tions of temperature, or the presence of impurities, may render a 
metal absolutely useless. Welding is the property, possessed by 
metals which, on cooling from the molten state, pass through a 
plastic stage before becoming perfectly solid, of being joined together 
by the cohesion of the molecules introduced by the application of an 
extraneous force, such as hammering. This property is exhibited 
in a marked degree by iron and platinum at a white heat. 

All steel is iron, differing only in containing a larger percentage 
of carbon, usually with a small quantity of silicon and manganese, 

8 



114 MODERN METHODS OF WELDING 

and often a small percentage of some other metal. What is known 
as mild steel is a product that stands between wrought iron and the 
hardest steel, as that used for making cutting tools. This mild 
steel has largely taken the place of wrought iron and is used in the 
construction of steel buildings. Pure iron is a soft, greyish-white 
metal, very ductile and malleable, and highly tenacious. This is 
generally used as welding iron. After fusion, pure iron exhibits 
a crystalline scaly fracture. It is softer than wrought iron, and is 
not affected by heating to redness and quenching in cold water. 
It is highly magnetic, and welds readily. Its specific heat is 0T13 
and its specific gravity 7-675. It melts to a lower temperature than 
platinum, about 1,600° C. In mass it is unaffected by dry or moist 
air, and more so in oxygen, yielding a scaly coating of oxide. When 
molten, it dissolves or occludes various gases in considerable quan- 
tities. Hydrogen, carbon monoxide, and nitrogen are thus taken 
up and given out on cooling. 

The above physical properties are present in a greater or less 
degree in cast or wrought iron and steel, the extent to which they are 
modified depending on the purity of the substance. These bodies 
consist of iron containing varying proportions of carbon, silicon, 
manganese, sulphur, phosphorus, etc. The main difference between 
the properties of cast and wrought iron and steel are due to the 
presence of carbon in the metal, depending on the amount and the 
manner in which it exists in the iron. The maximum amount of 
carbon taken up by pure iron is stated to be 0-475 per cent. In 
cast iron containing manganese, a little over 5 per cent, may be 
present. Steel may contain up to 1-8 per cent., while the carbon in 
wrought iron seldom exceeds 0-25 per cent, and may fall as low as 
0-05 per cent. 

The designation of steel was formerly confined to those varieties 
of iron which could be hardened by heating to redness and plung- 
ing in cold water. The introduction of the Bessemer process marked 
a new era. The metal produced by that process lacks the fibrous 
character associated with wrought iron and partakes more or less 
of the character of steel. Varieties possessing more than 0-3 per 
cent, of carbon sensibly harden when treated in the same manner 
as steel. Some steels are even softer than wrought iron. Since the 
hardening property is dependent on the amount of carbon contained, 
a classification based on the percentage of that element is most 
convenient. Steel containing less than 0-5 per cent, is classed as mild 
steel. The different nature of the metals may be shown by the use 
of such titles as Bessemer, Siemens, or open-hearth steel. Some 



IRON AND STEEL 115 

of these contain as little as 0-08 per cent, of carbon — less than is often 
present in wrought iron. (This is the easiest of all steels to weld, 
but very little of it is manufactured, not being the usual standard.) 
They differ from wrought iron in being devoid of fibre, more homo- 
geneous, and, unlike it, are obtained in a state of fusion. 

The fracture of steel becomes finer the larger proportion of 
carbon present, but it is affected by such treatment as hammering. 

Cold steel of hard temper breaks with a clear, uniform, grey, 
fine, granular fracture. After hardening, the colour is somewhat 
whiter. It is very malleable, but requires working more carefully 
and at a lower temperature than wrought iron. Steel containing 
less than 1-25 per cent, of carbon can be welded, but at a lower 
temperature than wrought iron, or the steel will be burnt. To 
render the surfaces clean at the lower heat, borax mixed with 
one-tenth of its weight of sal ammoniac should be employed to 
dissolve the scale. 

The specific gravity of steel varies from 7-624 to 7-813. The 
melting-point varies with the proportion of carbon. The softest 
melts a little below 1,600° C. The tenacity varies from 22 tons in 
mild steel to 70 tons in steel of hard temper. The elasticity exceeds 
that of wrought iron, while the ductility is equal to the best qualities 
of that substance. The mild varieties suffer an elongation and 
diminution in area when subject to a stretching force greater than 
wrought iron. The elongation of the harder varieties is much less, 
but the elastic limit is high. Mild steels, when being welded and 
becoming molten at the weld, are liable to " bod." This is due to the 
disengagement of dissolved gases, mainly H, N, and CO, which are 
given up as the metal cools off. The bubbles of the gas cause the 
metal to be honeycombed and vascular. 

Tenacity of metal is determined by straining a piece of metal 
of known dimensions, and observing the amount of force necessary 
to fracture it. Elongation, the extent to which a metal elongates 
prior to fracture, is a matter of greatest importance. Tough ductile 
metals show a considerable increase in length ; hard, brittle metals 
elongate but little. Important evidence as to the working qualities 
of the material and efficiency of the weld is furnished. To deter- 
mine the elongation, the test-piece is measured between the points 
at which it is gripped before and after straining till fractured (it is 
usual to put two marks on the test-piece for measuring), and the 
increase is stated in percentage of the original length. Thus a 
10-inch test-piece of boiler steel measured 12-5 inches after fracture 
— i.e., 2-5 inches over 10 inches, or 25 per cent. Elongation is 



116 MODERN METHODS OF WELDING 

accompanied by a diminution in area of section. This is measured 
in order to determine whether the elongation was local or uniformly 
distributed. Sometimes the contraction in area is confined to the 
region of the fracture. 

Some Difficulties in Welding. 

Welds on mild steel, which apparently are the most easy to 
obtain, are in reality those which require the greatest study and 
skill on the part of the operator. The welding must be done to give 
the weld the mechanical properties approaching those of the metal 
to be welded. In cases where the process is applied without the 
knowledge of the technique, the strength of the metal and, above 
all, its elongation are considerably lowered. In short, the operation 
of welding can lower, at the line of joining, the principal qualities of 
mild steel, which are particularly required in metallic construction. 

If the operator will go thoroughly through the chapter on iron and 
steel, he will learn much that will be of great assistance to him in 
his welding. One of the important things to remember in welding 
iron and steel is the formation of the oxide and its inclusion in the 
metal forming blowholes. It is to be noted that there is always 
a formation of oxide at the surface of the iron and steel melted under 
the action of the blowpipe. This oxide fuses before the metal, and 
is lighter. Therefore it rises to the surface of the metal when molten, 
and can be eliminated by passing the welding-rod in a horizontal 
position over the weld while the metal is molten. Steel and iron 
in a molten state dissolve 1-1 per cent, of oxide. This is always the 
case, and unless the operator has full knowledge of the technical 
and metallurgical points, he prevents the joints standing the stresses 
required. The technique of oxy-acetylene welding is very little 
known, and there are yet many problems to be discovered. 

Many operators make the frequent mistake of interposing 
oxide in the weld. In nearly all these cases this is caused by burn- 
ing of the weld, when an excess of oxygen is used, the flame held 
on the weld too long, and too large a surface liquid. It causes the 
weld to become " cinderised." In the melting period of the weld the 
suspended particles are no doubt due to the spitting of the metal as it 
fuses, but the origin of the oxide when the molten metal is covered 
with the slag is less certain. It may possibly be due to the presence 
of iron vapour in numerous bubbles of carbon monoxide formed 
throughout the molten weld; or probably to the spurting of the 
molten metal. The oxide defuses in the molten metal, and reaction 
takes place with the carbon and manganese and reduces their 



IRON AND STEEL 



in 



strength. The dissolving of the gases may be given up, if the 
operators take care, when the metal is molten, to allow these gases 
to escape, and to make good solid welds. 

One fault, of which many operators are guilty, is to use a toe 
high-powered blowpipe, or to use too high pressure of oxygen, whict 
causes an over-fierce flame. Consequently the metal has not time 
to get thoroughly hot before it begins to become liquid. Onlj 
just the surface is "swilled," and the underneath layer is no1 
anywhere near the welding-point. This is the cause of many defec- 
tive welds in which there is adhesion and oxide is interposed in the 
weld. 

a: 






\ r 





Fig. 61. — Tension al Tests, Welded Flat and Bars. 



This can be avoided if the proper-sized blowpipe is used, and the 
pressure of oxygen is that prescribed by the makers of the blowpipe, 
and no more. Then the weld must be proceeded with at a moderate 
speed, giving time for the edges of the article to melt thoroughly 
into a thick liquid form. Then the feeding-rod must be added and 
the weld filled up. The blowpipe must not be allowed to remain on 
the metal after it has been melted (and the tip must be kej3t about 
yV inch from the metal that is being welded) as it burns the metal 
after the first melting. If the metal gets too hot, it becomes too 
liquid and is burnt, and the carbon and other elements are partly 
destroyed, thereby reducing the strength of the weld considerably. 



118 MODERN METHODS OE WELDING 

rhe point of the molten metal should be just a thick liquid, and 
mould never be made hotter or thinner liquid, which causes oxida- 
:ion and swilling. 

The author would draw attention again to his previous remarks 
is to operators testing their work from time to time. Leading 
mgineers, through so many past failures, and so many bad and 
defective welds, are not very favourable to allowing oxy-acetylene 
welding to be done on anything that has to stand any great stresses. 
rherefore operators should, without fail, make repeated tests from 
;ample welded joints, as outlined in previous chapters. In addition 
:o the tests explained, tensional, distortional, and other mechanical 
bests can be made, and will greatly assist operators in becoming 
efficient. These latter tests many schools would be glad to make 
m their behalf. 

Blowpipes must be the best, if good welding is required. The 
previous chapter on the subject has laid this down; a further 
paragraph will help to emphasise their importance. Absolutely 
bhe best blowpipe must be procured, irrespective of cost. In the 
selection the following points should be considered: The blowpipe 
must have a constant clear flame with a distinct white cone, as large 
is possible and sharp-edged ; must be easy of regulation ; must not 
back-fire. There must be a proper mixture of the gases at the nozzle 
Dutlet, and at the correct pressure specified by makers, and no more, 
rhere must be no excess of acetylene (which carbonises), no excess 
Df oxygen (which oxidises). The latter in excess is most dangerous. 
In no case must a hard or steel wire be used for cleaning out the 
blowpipe nozzle. A piece of copper wire would suit. If the nozzle 
3f the blowpipe is only minutely enlarged, it causes disarrangement, 
and the blowpipe does not work satisfactorily. 

Welding-rods for use on iron and steel are composed of pure 
iron in the form of wire, in the various sizes for the thickness of metal 
welds. By using a pure iron rod, the line of weld will also be pure 
(providing the welding has not been oxidised). All metallurgists 
ire fighting against the inclusion of phosphorus, sulphur, and silicon 
in the manufacturing of steel and iron ; therefore operators must 
also fight against allowing these impurities to find their way into a 
weld. A good flux for iron and steel is as follows : 

\ 



Borax . . . . 3 parts 

Colophony . . . . 2 ,, 

Pulverised glass . . 3 ,, 
Steel filings . . . . 2 ,, 
Carbonate of potash 1 part I 
Hard soap powder . . 1 „ • / 



r Melt in an earthenware vessel. 



IRON AND STEEL 119 

One cannot be too particular in preventing these impurities in 
the welding line. None but the purest rods must be employed. 
They are to be got if the price is paid. One must not expect to 
obtain pure charcoal wire without paying for the purity. The extra 
cost is saved in many ways. The welding is faster, very much 
stronger, and almost free from oxide. There is no going over the 
weld twice, and no burning, as it melts freely. Finally, the weld is 
neater. 



CHAPTER XXI 
CAST IRON 

Cast iron is the cheapest and most abundant form in which metal 
is met with in commerce. It is fusible at a temperature which can 
readily be attained ; and, as it receives remarkably clean and exact 
impressions of a mould, it can be cheaply produced, even in very 
intricate forms. Its tensile strength, varying from an average of 
about 7 tons per square inch in common castings to upwards of 
15 tons with special mixtures, is ample for many purposes. Its 
crushing strength is greater than any other material, reaching a 
maximum of about 100 tons per square inch. Being protected by a 
skin, cast iron resists atmospheric influences better than wrought 
iron or steel, while, for wearing surfaces for machinery, nothing is 
superior to cast iron on cast iron as sufficient area is provided. 

Castings are much more easily and cheaply produced than forg- 
ings, so that the latter are only employed where special requirements 
or strength and ductility render their adoption necessary. As 
compared with steel castings, the advantages of cast iron for ordinary 
uses include not only the cheapness of the original material, but also 
the diminished cost in the preparation of the moulds, the smaller 
loss in casting, and the saving of expense and the time required for 
annealing, which is necessary for steel, but not for cast iron. Iron 
castings can, therefore, be prepared to meet a pressing emergency, 
while their fine surfaces, sharp edges, and pleasing appearance 
recommend them for general use. It must be noted that, in the 
welding of castings, one must not go over the weld twice, as it has 
an oxidising effect on remelting, and the portion of the silicon is 
diminished, while the sulphur is at the same time absorbed from the 
blowpipe gases. The natural effect of these changes is shown in 
the condition of the carbon, which, instead of being almost wholly 
graphitic, is all combined, thus producing a hard, white iron, deficient 
in tenacity, and brittle. The physical effects produced when cast 
iron is remelted are thus merely indications of chemical changes 
which have taken place in the material, whilst the nature of these 
changes will vary with the composition of the iron employed. 

120 



CAST IRON 



121 



Effect of Size and Shape. — -The strength and solidity of a casting 
are affected by the bulk of metal employed, and by the form of the 
casting made. When the metal cools in a mould, a crystalline is 
developed, the crystals forming at right angles to the cooling surface. 
If this cooling surface be curved, the crystals interlace, so as to yield 
a strong uniform structure, while, on the other hand, whenever a 
sharp change of curvature takes place, a plane of weakness is 
developed. 

Shrinkage of Cast Iron. — -Although cast iron, especially when very 
grey, expands at the moment of solidification, the subsequent cooling 




Fig. 62. — Tramway Gear Case, Outside Bearing Broken Off, Successfully 

Welded. 

from a red heat to the ordinary temperature leads to a still greater 
contraction. The shrinkage of castings is, however, by no means 
a constant quality, but varies with the proportions of the castings 
and with the character of the metal used. 

Hardness of Iron. — The hardness or softness of cast iron is, in 
many instances, of the greatest importance, as the metal has to be 
turned, planed, filed, or otherwise worked with tools. When cast 
iron has to be turned or otherwise worked, the hardness is of con- 
siderable importance, while in some cases smoothness of surface 
and general perfection of the casting are of the utmost moment. 
Hard cast iron is brittle, deficient alike in crushing, transverse, and 
tensile strength, and seldom gives good clean castings. 



122 



MODERN METHODS OF WELDING 




Fig. 63. — Press Frame Broken on One Side, 
and Patched with Two 2-Inch Bolts. 

Bolts failed and welding was necessary. 



When cast iron cools from fusion, the carbon may remain 
uniformly distributed through the mass- — combined carbon — or a 
portion of it may separate out in scales resembling graphite. The 
extent to which separation occurs depends on the rate of cooling 

and the quality of the metal. 
Slow cooling, and thepresence 
of silicon and aluminium in 
the metal, favour the separa- 
tion, while manganese re- 
tards it. 

When rapidly cooled, 
nearly all the carbon remains 
in the combined form. 

Combined carbon hardens 
the metal, lowers its melting- 
point, destroys its mallea- 
bility and welding power, 
and tends to make it brittle. 
The extent to which these 
effects are produced depends 
on the amount. In white cast iron containing as much as 3 per cent., 
the metal is brittle, breaks with a silvery-white fracture, melts-more 
readily, and passes through a pasty stage in fusing. It is extremely 

hard, and this property isper- 
manent. In steel for cutting 
instruments, the amount 
varies from 0-5 to 1-5 per 
cent. The hardness and 
fusibility are increased, the 
malleability and the welding 
power reduced, in proportion 
to the amount of carbon 
present. 

Graphitic carbon is met 
only in cast iron, and occa- 
sionally in steel. It reduces 
the strength of the metal by 
interposition between the 
particles, but does not affect 
the grains of the irons themselves. The generalisation above as to 
combined and free carbon only expresses part of the truth. When 
white cast irons, free from manganese, are heated for a long period, 




Fig. 64. — Press Frame Welded at Cost 
of £9 7s. 6d. Weld 3 Feet Long and 
1 Inch Thick. 

In use for the past two and a half years. 



CAST IRON 123 

at a high temperature, but below fusion, embedded in red hematite, 
the characteristic brittleness is lost, and they become more or less 
malleable. 

In connection with the influence of cooling, cast iron obeys the 
laws which govern other solutions, for it is well known that slow 
cooling assists the production of crystals, and leads to the production 
of larger size, while with rapid cooling both solvent and substance 
dissolved may solidify together. In a similar manner slow cooling 
tends to produce graphitic carbon, and the slower the cooling the 
larger the flakes of graphite which separate. Some kinds of white 
iron may thus be rendered grey by slow cooling, while some kinds 
of grey iron may be made perfectly white by rapid cooling or 
" chilling." 

That the carbon which exists in grey iron is in the graphitic form 
can be proved by many simple tests. Thus, if finely divided white 
iron be rubbed between the fingers, it is clean to the touch, while grey 
iron produces a smooth black coaling on the skin, exactly like that 
due to plumbago. It has been shown that nearly pure graphite 
can be separated from grey iron. 

All cast irons contain silicon, in quantities varying in ordinary 
cases from under 0-5 to over 4 per cent. A small addition of silicon 
eliminates blowholes, and produces sound castings. As soon as the 
metal is sound, with the least graphite, the greatest crushing strength 
is obtained. This condition also gives the maximum density. 
The further addition of silicon leads to graphitic formation, 
diminishes the brittleness, and gives the greatest transverse and 
tensile strength. White iron shrinks during solidification more than 
grey iron, while highly siliceous iron shrinks still more than white. 
Hence, on adding silicon to white iron, the shrinkage is diminished ; 
but an excess of silicon, on the other hand, leads to increased 
shrinkage. Shrinkage appears closely to follow the hardness of cast 
iron, hard irons almost invariably shrinking most; and as hardness 
and shrinkage depend upon the proportion of carbon, they may be 
regulated by a suitable addition of silicon. 

Cast iron is a granular and crystalline compound of iron and 
carbon, more or less mixed with uncombined carbon in the form 
of graphite, but never contains more than 5 per cent. It is harder 
than pure iron, most brittle, and not so tough. The modes of com- 
bination of the carbon with the metal, as well as the nature and 
proportion of foreign matters, such as silicon, aluminium, sulphur, 
phosphorus, and manganese, determine the infinitely varying quali- 
ties according to the colour, degree of fusibility, hardness, tenacity, 



124 MODERN METHODS OE WELDING 

and so on. All cast irons are not available for foundry purposes. 
In grey cast iron the carbon is mechanically interspersed in small 
black specks among the lighter particles of metals, the fracture being 
a dark grey colour, and being of granular or scaly crystalline char- 
acter. Grey iron is much softer and tougher than white iron, and 
may be filed and turned. 

In white cast iron the greater part of the carbon is present in 
the form of a chemical combination — carbide of iron — and white 
iron is very brittle, and can neither be turned in a lathe nor filed. 
Grey cast iron requires a higher degree of heat before it commences 
to fuse, but becomes very liquid at a sufficiently high temperature. 
It is important to remember this point when castings are being 
welded, especially when inclined from the horizontal, as the metal 
would run away from the weld. White cast iron is not so easy tc 
weld. It does not flow well, is rather pasty in consistence, and scintil- 
lates as it flows in the molten state. White cast iron is silvery- 
white, either granular or crystalline, difficult to melt, brittle, and 
excessively hard. It is a homogeneous chemical compound of iron 
with from 2 to 4 per cent, of carbon. Granular cast iron can be con- 
verted into grey cast iron by fusion and slow cooling, whilst grey 
cast iron can be converted into granular white cast iron by fusior 
and sudden cooling. Crystalline white iron is harder and more 
brittle than granular, and is not capable of being converted into 
grey cast iron. Grey cast iron contains about 1 per cent., or less. 
of carbon in chemical combination with the iron, and from 1 to 4 
per cent, of carbon in the state of graphite in mechanical mixture. 
The larger the proportion of graphite the weaker and more pliable 
is the iron. 

The following remarks upon some points already described may 
aid in roughly estimating the quality of cast iron. 

When the colour is uniform dark grey, the iron is tough, providing 
there is also high metallic lustre. If there be no metallic lustre the 
iron will be easily crumbled. The weakest sort of cast iron is where 
the fracture is of dark colour, mottled, and without lustre. The 
iron may be accounted hard, tenacious, and stiff when the colour 
of the fracture is lightest grey, with a high metallic lustre. When 
the colour is light grey, without metallic lustre, the iron is hard and 
brittle. When the colour is dull white, the iron is still more hard 
and brittle than in the last case. When the fracture is greyish- 
white, interspersed with small radiating crystals, the iron is of the 
extreme degree of hardness and brittleness. 

When cast iron is dissolved in muriate of lime or muriate of mag- 



CAST IRON 125 

nesia, the specific gravity is reduced to 2-155. Most of the iron is 
removed, and the remainder consists of graphite with the impurities 
of cast iron. The soft grey iron yields to the hie after the outer 
crust has been removed. The quality of the iron in a melted state 
is really judged by the practised eye from the nature of the agitated 
aspect of its surface. The mass of fluid seems to undergo a circula- 
tion within itself, having the appearance of ever-varying network. 

When this network is minutely subdivided, it indicates soft iron. 
If, on the other hand, crystals be thrown up in convolutions, the 
quality of the metal must be hard. 

One of the most important points in the welding of cast iron 
is not to go over the weld twice, as each time any part is melted 
more than once, the graphite burns out and leaves white iron, which 
is hard and brittle. One must remember that every additional 
melting of cast iron injures, or is likely to injure, its quality as a 
structural material by the addition of foreign substances. These 
reduce the value of the coefficient of resistance at rupture and may, 
or may not, reduce that of ultimate extension. That is, the metal 
by remelting becomes weaker, and may become more brittle. 

The numerous failures which puzzle operators in the welding of 
cast-iron articles are often due to lack of knowledge. They have 
not made themselves acquainted with the metal they are welding. 
It is a sine qua non that, if they are to become proficient operators, 
they must have the necessary metallurgical knowledge, so as to 
know exactly what are the constituents of the metal being welded. 
The state of the carbon in the metals depends on whether welds are 
of grey iron. It is necessary for every welder to study thoroughly 
the causes that facilitate or prevent the precipitation of the carbon 
in the form of graphite. The rapid cooling of the molten metal in 
fusion will bring about the combination of the carbon and the iron. 
This forms white iron, which is hard and brittle, and cannot be 
machined or filed. 

Welding of cast iron is a simple process, and with an experienced 
man, who has knowledge — -metallurgical and chemical — of the 
article he has to weld, failure is impossible. The repair on the fine 
of welding is generally of a superior quality to the rest of the casting, 
owing to the metal added being purer and the weld well carried 
out and free from blowholes. Cast iron consists of metallic iron, 
together with at least 1-5 per cent, of carbon. It also contains 
sulphur, silicon, phosphorus, manganese, and other elements in 
greater or less proportion; but these, as indicated above, may be 
regarded as impurities. The proportion of elements other than 



126 MODERN METHODS OF WELDING 

iron is usually about 7 per cent, of the total weight. Cast iron is 
fusible at a temperature of about 1,200° C. When cold it is hard 
and brittle. It is not malleable or ductile, nor can it be hardened 
or tempered like ordinary carbon steel. Cast iron, when fused, con- 
sists of saturated, or nearly saturated, solution of carbon in iron. 
The amount of carbon which molten iron can thus dissolve is about 
3 J per cent, of its own weight, though the solubility is largely in- 
fluenced by the presence of other elements. As long as iron con- 
taining some 3 per cent, of carbon remains in the fused condition, the 
composition is uniform throughout, and the carbon has no tendency 
to separate from the metal except with very grey iron. In this case 
a layer of graphite may be formed. But when molten cast iron is 
cooled to a temperature at which it begins to solidify, it may either 
retain the carbon and solidify in a relatively homogeneous form, 
called white iron, or may, in solidifying, precipitate the greater part 
of the carbon in the form of small scales of graphite which, being 
entangled by, and uniformly distributed through, the iron, imparts 
to it a somewhat spongy nature, and produces the dark colour and 
soft character met with in grey iron. The condition which the 
carbon assumes on the solidification of the mass is dependent partly 
on the rate of cooling, and still more on the nature and quantity of 
the associated elements. 

In the early stages of the oxy-acetylene process it was generally 
considered that cast iron and cast steel could not be welded by this 
process. The author, over fifteen years ago, welded castings by this 
process nearly daily, and executed some very important castings 
with success. At this period he found out how valuable and neces- 
sary was the preheating furnace for counteracting the phenomenon 
of expansion and contraction. Since then it has been recognised 
that the only way of getting satisfactory castings welded is by the 
use of a heating furnace, both for preheating before welding and 
for annealing after welding, allowing the casting to cool very slowly 
Failure is almost impossible if this is carried out, provided the weld 
has been properly executed. 

Of late years operators and employers have been getting more 
enlightened on welding processes, and most are now providing these 
necessary appliances. Also all operators are now taking technica 
courses at the various schools. Cast iron, in the author's opinion 
is the easiest of all metals to weld. With a little practice, combinec 
with technical knowledge, operators are soon able to do intricat< 
jobs; and the welded part, if done well, is generally better than th< 
other parts of the casting, because the material added by the weld 



CAST IRON 127 

ing-rod is purer in its mixture, and should thus be better metal. 
Cast iron cannot be forged, but articles are cast. They are not malle- 
able or ductile. The majority of castings in iron should be capable 
of being worked — that is, they must be soft metal when finished 
and able to be filed or machined. The metal of grey castings is 
usually grey iron. The description at the beginning of this article 
should be studied thoroughly. One must remember that the rapid 
cooling of the metal in fusion brings about the combination of the 
carbon and the iron, which means the formation of white iron. 
Slow cooling and reheating bring about precipitation of the carbon 
and grey iron. 

The melting-point of cast iron is 1,200° C, but its oxide melts 
at 1,350° C. This is an important point, and in melting, the oxide 
usually flows on the top of the weld, where it can be removed either 
by a flux or (if the welder be experienced) by the welding-rod, 
scraping it over the surface horizontally. If the flame is held too 
long on the casting after the metal is molten, the metal burns and 
oxidises, the silicon is volatilised, the carbon decarbonised, and the 
weld will be hard and cannot be machined or filed. When cast- 
iron articles are welded the welding flame causes, to a certain extent, 
a volatilisation of the silicon, which is contained in the metal in 
proportion from 0-5 to 4 per cent., generally about 2 per cent. 
If this is burnt out, it is necessary to replace the loss, which is done 
by the welding-rod, which should contain 5 per cent, of silicon. 
Therefore, as welding takes place, the rod with the increased per- 
centage of silicon gives back to the casting the percentage that has 
been volatilised out. This material usually leaves the welded line 
soft, so that it may be machined or filed. 

Of the difficulties experienced, the first is the expansion and con- 
traction. Owing to the metal being non-ductile, and devoid of those 
elements for elongation and elasticity, castings are difficult to handle. 
The only remedy is preheating in a furnace, and annealing after 
welding. 

The second difficulty is to prevent the line of welding becoming 
hard. To stop this the weld must be made at the first trial, and 
must not be gone over a second time. The welding must also be 
sharp, as, if the blowpipe is kept on too long, it is burnt and the 
weld hard. 

Thirdly, the temperature of the casting must be brought up in 
the furnace to between 850° and 900° C. before any welding takes 
place. If it is lifted from the furnace to the welding table, it 
must be done quickly, and quickly welded, and returned to the 



128 MODERN METHODS OF WELDING 

annealing furnace before the heat of the casting gets below the 
850° C. Below this temperature the forces of expansion and 
contraction begin to come into action, and internal strains will 
at once be set up, which may, in a few minutes, if the tempera- 
ture is much below 850° C, crack or fracture in the casting; it is 
not necessary in the weld. In some cases, the internal strains remain 
in the castings without fracture, until the casting becomes quite 
cold, when the fracture from the release of the internal strains occurs. 

After welding, and putting the casting into the furnace, it must 
at once be seen to that the temperature of the furnace is raised (if it 
is not already raised as it should be) to 950° C. This is so that the 
casting after welding can be raised to this heat quickly, to bring 
the parts of it up to one heat, since the part that bad been welded 
was very much hotter than the part not welded. Thus one can stop 
uneven contraction when the casting is being cooled off. After 
the heat has been raised to 950° C, which would not be long if the 
furnace is working as it ought to, the furnace must be cooled right 
down to cold before removing the casting. 

Some illustrations of preheating and annealing are given in 
previous chapters relating to expansion and contraction. They 
should be carefully studied. 

Fourthly come the difficulties of lack of penetration, bad joining, 
sinking of the surfaces, blowholes, and interposition of oxide. 
Lack of penetration is a frequent occurrence. There is, however, 
no justification for it, if operators will only go to the bottom of the 
weld in all cases. The blowjnpe must be kept on the particular 
welding line, until such time as the bottom is melted. When the 
bottom is found at the starting-point, there should be no mistake 
about the line being continued from the bottom of the weld. 

Interposition of oxide is a common occurrence, but it is one which 
can easily be avoided. It occurs through using an excess of oxygen, 
making the molten metal oxidised too liquid and too hot, and 
through being too long on welding and going over it more than once. 
The oxide forming through these errors is imprisoned in the metal. 
Therefore, it is not homogeneous, and the weld is defective. This 
will not come about if the operator will first of all bevel the joint 
where it has to be welded. When it is ready and heated, welding 
must take place at once by commencing on the bottom of the bevel. 
As soon as this is melted, add the welding-rod, previously heated, 
in the bevel, move the blowpipe forward with an elliptical sweep, 
keeping it close in the line of metal. Do not let the white tip touch 
the metal, but keep it about ^ inch from it, and go steadily and 



CAST IRON 



129 



slowly forward, filling up the bevel uniformly with the feeding- 
rod until the end of the weld is reached. There must be no stoppage 
whatever, while welding the line prepared. If you stop, your 
weld will be hard and cannot be filed or machined. If it is done 
quickly, and filled in as the welding proceeds, with no stoppage, 
the weld will be a success, neat, strong, and easy to work. 

If the article to be welded is a complete casting with a break, 
then it would be necessary to bevel the fracture on both sides before 
welding: such a case is a motor cylinder broken on the flanges. 
The one illustration below would require bevelling; and take care 
that the weld is thoroughly penetrated. 

Welding-rods used for cast iron should be made more or less 
from good tough metal, 
with a fine granular 
structure, and free from 
impurities, especially 
manganese. They 
should be incorporated 
with silicon, in two 
grades, one to have 2-9 
per cent, and the other 
to have 4-1 per cent, 
of silicon. The object 
of this grading is very 
important, as the one 
has a large granular 
structure, and the other 

has a fine granular structure. The latter would be used on heavy 
machinery work, and the former on smaller castings, such as motor- 
car cylinders, which are cast from fine granular material. 

All founders grade their metal in this manner. They do not 
use the same for both light and heavy castings. Therefore it 
is imperative that the welding-rods should be made in accordance 
with the general specifications of the general castings; and they 
should be very smooth and regular in thickness, which should be 
from | inch diameter rising by T X g inch diameter to | inch diameter. 

They should be 20 inches long, and should be all sand-blasted, 
after they are cast. This is an important point. Otherwise the rods 
will be all rough and covered with sand, which is very detrimental 
to the weld. No welding -rods must be used which have not had 
the moulding sand removed; nor must welding-rods be used that 
have been cast in solid moulds, as they would be chilled and hard. 

9 




Fig. 65. — Two-Cylinder Motor Engine Broken. 



130 



MODERN METHODS OF WELDING 



It is not agreed in the welding trade that fluxes are necessary 
for the oxy-acetylene welding of cast iron. The author does not 
advise the use of any flux whatever, in general. But there are a few 
cases in which a flux is of great assistance — e.g., where castings are 
old, or are full of sand and slag. This will only occur where cheap 
castings are made. The method of using the flux is to dip the 
end of the rod into flux, which should be near to hand and to the rod 
being heated. The flux must not be thrown into the molten weld, 
as too much would make the weld hard, so that it could not be 
worked. 

The illustration (Fig. 67) shows a good test of cast-iron welding 
— a water pump accidentally broken while being worked in the 

shop. It was welded in thirty-six 
minutes. 

The method of execution was as 
follows: The casting was first bevelled 
with a diamond-point chisel, the metal 
being ~- tJ inch thick. The gas furnace 
had already been lit. The casting was 
placed on a sliding grid, which fitted on 
the sides of the furnace. This sliding 
grid, with casting placed and fixed in 
position, was lifted by a small swinging 
hand-crane, hoisted by a rope, and 
swung round to the furnace, when the 
grid was pushed into the furnace. The 
casting was covered with an asbestos 
"shawl," and the door closed. The tem- 
perature was then at 550° C. Another 
burner was lit, and the temperature rose to 950° C. in thirty-five 
minutes Half the burners were put out, and the sliding grid, with the 
casting still fixed, was lifted by the crane and placed on the welding 
table. The blowpipe, already in position, was lit, and the welding 
started, and was continued without interruption or without going 
over any part of the weld twice. The grid was then attached to the 
crane, which swung the casting back to the furnace. The door was 
closed and the two burners lit till the temperature (then 800° C.) was 
raised to 950° C. (this occupied only thirty-six minutes from the 
time the furnace door opened to take it out till the door closed for 
annealing). Then the burners were turned right out, and the cast- 
ing was allowed to cool slowly overnight. The result was a first- 
class job, strong, well-annealed, and with no distortion. 



^Hb£?B KlM 



Fig. 66. — Two Cylinders 
Welded Complete. 



CAST IRON 131 

The field for welding such castings is enormous. The demand 
is greater than the supply. There are few operators able to do all 
jobs as they come along. If they had scientific and technical train- 
ing, which should be followed up with practical work, they would 
become proficient, and would be able to do any class of work. The 
possibilities of welding broken castings are great, and almost any 
repair can be done. A few articles here are shown which can be and 
have been welded by this process. Good jobs can always be done if 




Fig. 67. — Broken Two-Cylinder Water Pump. 

operators carry out carefully the instructions given. I may repeat 
that in all cast-iron weldings, if success is to be attained, the article 
must first be prepared, must be preheated (free from air) to a tempera- 
ture of 950° C, welded with the purest welding-rod, returned to the 
annealing furnace when the casting gets down to 850° C, whether 
the casting is finished or not, and, if it is necessary to weld further, 
must be brought up again to a temperature of 950° C. It can be 
taken out for welding, and afterwards returned to the furnace and 
allowed to cool slowly, free from air. 



CHAPTER XXII 
DISSOLVED ACETYLENE 

Dissolved acetylene, sometimes called high-pressure acetylene, 
is being greatly used, owing to its convenience, the purity of its 
acetylene, the equal pressure and proper mixture of the two gases. 
the regularity of flame, the absence of oxidising or carbonising, the 
well-maintained sharp cone at the tip, and the continuous welding 
till the cylinder is empty. 

Dissolved acetylene is acetylene in its purest form, compressed 
after purification into cylinders containing an absorbent material. 
The gas is first generated in an ordinary carbide-to-water type in 
which the carbide falls in large volumes of water in order to prevent 
overheating of the gas and to maintain within the generator a tem- 
perature considerably below that at which local polymerisation of 
the gas can occur. Otherwise the heat of dissociation, which repre- 
sents 1«65 per cent, of the total heating value of the gas, and is 
responsible for the phenomenal heating value of the acetylene flame, 
is liberated either wholly or in part during generation, and is there- 
fore not available in the flame ; in that case further local polymerisa- 
tion takes place, and the tarry residues mix with the water and the 
gas and make the latter impure. The acetylene, after generation, 
must be treated by numerous processes in order to extract the impuri- 
ties. These impurities are in three forms — gaseous, liquid, and solid. 
There is no single process capable of dealing effectively with the 
three. The gases must be treated with at least six processes of 
purification, two of which must be mechanical, four chemical. 
All chemicals must be incapable of producing overheating of the 
acetylene undergoing purification. Special precautions must, at 
all times, be maintained to preclude the possible admixture of air 
with the acetylene. All purifiers and the acetylene, after purifica- 
tion, should be tested twice daily in order to secure complete 
purification. 

The acetylene is then compressed into cylinders already prepared 
with solvent material. The compressors used for this purpose are 
multiple stage compressors, with intermediate cooling between 

132 



DISSOLVED ACETYLENE 



133 



each stage. The cylinders of the compressors must be water- 
jacketed, and the degree of compression in each stage must not be 
capable of raising the temperature in excess of 100° C. — that is, 
one-sixth of the critical temperature. The gas, after compression, 
and prior to entering the cylinders, must undergo mechanical separa- 
tion for the extraction of final traces of moisture. 

Cylinders in which dissolved acetylene is stored are made from 
the finest quality steel, and is cold-drawn to the shape of the cylinder 
from a flat piece of steel, whilst the bottom and walls are folded over 
one another and pressed together under a pressure of several tons 
per square inch. Only the finest and most 
ductile quality of steel would permit of 
cold-drawing for 44 inches in length. The 
cylinder walls, only f\ inch thick, although 
only intended for use under a pressure of 
about 200 pounds per square inch, are made 
to stand a pressure of 1,000 pounds per 
square inch. As is well known, acetylene 
gases can only be stored under pressure 
with safety when dissolved in a solvent 
such as acetone, which must be absorbed 
by a porous material adapted to fill the 
space in the containing vessel. 

Government regulations require that 
the porosity of the absorbent material in Fig. 68 
the container shall not exceed 80 per cent., 
and shall be homogeneous through the 
material without any free gas space. In 
the past it has been customary to employ, 
as the absorbent body granulated, solid 
material such as charcoal, or an animal 
filament, such as silk, but these substances 
are subject to certain disadvantages. Granulated charcoal and other 
solid materials tend to disintegrate into dust by attrition of the par- 
ticles, if the container is subjected to repeated vibration or bumping. 
This disintegration creates free gas space and also dust particles, which 
are liable to blow forward with the gas and block the container valve 
or the nozzle of the blowpipe employed when the dissolved acetylene 
is used for welding. Silk, owing to its fibrous nature, does not dis- 
integrate, but, on the other hand, it is not sufficiently resilient to 
obviate packing, and saturated with the liquid solvent and subjected 
to repeated vibration and bumping. The consequence is that free 




Perfect Neutral 
Flame. 
When blowpipe is working 
properly, the length of the 
small white cone is as shown. 
In the patent " D.A." blow- 
pipe, the numbers on the tip 
correspond to the consump- 
tion of acetylene in litres per 
hour. 



134 MODERN METHODS OF WELDING 

gas space may be created after the container has once been packed 
to the prescribed porosity and put in use. 

There has since been patented an improved method of storing 
compressed acetylene gas. This patent was taken out by Thomas 
Gaskel Allen, of London, July 27, 1916. The object of the invention 
is to provide a new type of filling material, superior to that used in 
the past. According to the material employed, it is sometimes 
known as "kapok " (Javanese fibre), or Indian kapok. One form 
suitable for the purpose of this invention is the Eriodendron 
anfractuosum, but the invention covers any suitable variety of 
kapok. Using this material, a much smaller weight than previously 
is necessary to obtain a porosity of 805 in the container. 

Further, kapok has a tendency to swell when it absorbs the liquid 
solvent, thus precluding altogether the possibility of free gas space 
forming within the container after it has been once packed to the 
required porosity. On examination with the microscope, the central 
tube, filled with air, gives to fibres or kapok its very valuable light- 
ness. The fibres are absolutely impermeable by water, owing to 
the presence of wax with which the filaments are coated. They will 
support from thirty to thirty-five times their own weight in water. 
Ordinary cork will only float five times its weight. This special fibre, 
when used as a filling material, cannot disintegrate into dust, no 
free gas space can be created by constant vibration, and no dust can 
pass through the blowpipe. 

Dissolved acetylene compressed in cylinders provides a definite 
volume of acetylene of the highest purity, at a constant pressure, 
controlled by a regulator fixed on the oxygen cylinder valve. This, 
together with the oxygen in equal volumes and at equal pressures, 
gives a wide range for welding. The clear flame obtained is shown 
in Fig. 68. 

The cone should not be allowed to touch the metal, but should be 
held so that the required heat is obtained without burning the work. 
When stopping the blowpipe, always turn off the oxygen first. 
This system has many advantages over the low-pressure process. 
The gas is always ready for use without waste of time in preparation, 
and when shut off it can be stored indefinitely without loss. It is 
handled with the greatest ease, and can be used in any position. 
The apparatus is cheap ; the handling of carbide and water and the 
necessity of removal of residue are eliminated. There is no danger 
to the operator, and no bad smell, owing to the purity of the gas. 



CHAPTER XXIII 
CUTTING IRON AND STEEL 

The use of oxygen for cutting iron and steel is being developed 
enormously, and is being adopted everywhere. The method con- 
sists essentially in an ordinary blowpipe, with an additional passage 
through which an independent and separately controlled stream of 
oxygen is supplied at the discretion of the operator. This separate 
supply of oxygen may be discharged through the centre of the blow- 
pipe, in which case the mixed gases employed for heating are con- 
ducted through an annulus surrounding it; or the supply may be 
brought in a passage immediately behind the heating flame. 

The simple expedient of maintaining an independent heating 
jet in operation, whilst the cutter is travelling, renders the cutting 
operation continuous. It furnishes the quantity of additional heat 
necessary to render the oxide fluid, so that it can be blown away 
through the cut by the separate jet of oxygen. The cutting opera- 
tion can be mastered by any intelligent workman in a few hours. 
The edge or surface of the plate at the point to be cut is heated by the 
mixed jet of oxygen and acetylene. When this spot has been brought 
to a state lower than the melting-point, a fine jet of oxygen is dis- 
charged upon it. This immediately produces combustion of the 
metal, with the resulting formation of the oxide. The jet of oxygen 
is made sufficiently strong to blow away this oxide in front of it, 
with the result that a clean, narrow cut is effected through the metal 
at a speed of travel which is comparable with hot sawing. The 
metal on each side of the cut is neither melted nor injured in any 
way, as the action proceeds too rapidly for the heat to spread. 
In fact, the edges present the sharp and purely metallic surface of a 
saw cut. 

The cutting may be made to follow any desired lines, executing 
circles, curves, or profiles as desired, for which purposes guides and 
other mechanical contrivances are supplied. Special appliances are 
supplied for ensuring a steady movement of the cutting nozzle, 
a matter of considerable importance where neat and accurate work 
is desired. The process may be employed for cutting sections of any 

135 



136 MODERN METHODS OF WELDING 

thickness up to 16 or 20 inches. In metal cutting by oxygen, the 
melting-point of the metal should never be reached. The successful 
employment of oxygen for this purpose, therefore, depends on the 
melting-point of oxide being lower than that of the metal. 

The cutters are made in several varieties. The British Oxygen 
Company are makers of the one illustrated below, which is a 
" universal "; it is a reliable article and is largely used. 

Rubber tubing must be fixed at and H respectively. The 
gases for heating are separately adjusted by valves R and H. 
These mixed gases are discharged through the passages D. The 
valve regulating the supply of oxygen for cutting is separately 
controlled by means of the thumb screw Q or the thumb lever valve 
P. The separate jet of oxygen for cutting is discharged through 
the passage C. A is an adjustable sliding guide, which can be 




69. — Hand-Cutting Blowpipe. 



attached to the cutter head at B, in order to maintain a uniform 
distance between the cutter and the work. There are two nozzles — 
one for cutting up to 6 inches thick, and a spare one to cut over 
6 inches. The table on p. 137 gives the approximate results with 
various thicknesses, the consumption of oxygen, and lineal feet cut 
per hour, etc. 

This is a very useful table. Operators can compare results from 
their own cutting by it. 

Since the period in which oxygen was introduced the develop- 
ment has been rapid. Here, again, the war has brought this unique 
process into vast uses, which would have taken ten years of industrial 
work to attain. 

The real theory of oxygen cutting of iron and steel was a very 
simple process, and was known for years before it became a com- 
mercial proposition. It was found in the chemical laboratory that 
jf a thin strip of iron or steel is plunged into a jar of oxygen, after 



CUTTING IRON AND STEEL 



137 



being heated to redness, the iron ignites to incandescence and 
burns right away. This, then, is the equivalent to cutting steel by 
oxygen, as we shall see as we go along. 



Thickness 
of Plate. 


Size of 
Gutting 


Oxygen 
Pressure. 


Consumption 

of Oxygen 


Feet of 
Metal Cut 


Consumption 
of Oxygen 


Nozzle. 


per Hour. 


per Hour. 


per Foot Cut. 


Inches. 


Inches. 










i 


i 

"3 5" 


24 


48 


65 


0-75 


i 


1 
7)^" 


28 


60 


60 


1 


3 


J 


. 32 


75 


50 


1-5 


1 


t 

TB" 


32 


88 


40 


3-2 


H 


1 


36 


95 


35 


3-7 


U 


1 


39 


105 


30 


3-5 


2" 


1 


45 


125 


25 


5 


3 


1 


52 


180 


20 


9 


4 


1 

1 G" 


58 


300 


20 


15 


5 


1 

115" 


65 


420 


20 


21 


6 


1 
Tb" 


70 


432 


18 


24 


8 


"3"5" 


80 


504 


18 


28 


9 


S 
"5% 


95 


510 


17 


30 


11 


r 

"CT 


100 


620 


13 


48 


12 


7 
B"T 


125 


650 


13 


50 



Most metals oxidise under the action of the oxygen in the atmo- 
sphere, as is instanced by the rusting of iron exposed to the air. 
This is a form of oxide of iron. Upon the heating of the iron, the 
oxidation is very much more rapid and intense. Considering 
the method of cutting by a jet of oxygen, the object is to make the 
oxidation as intense as possible, so as to burn in the shortest time 
when in connection with the oxygen, and to obtain the narrowest 
cut possible. The oxidation takes place at the part which has pre- 
viously been heated to redness, because at this temperature reaction 
takes place readily. The combustion of this part of the iron dis- 
engages heat, a portion of which is absorbed by the neighbouring 
part. This is sufficient to raise it to a red heat, so that it in turn 
burns, and this reaction is progressively propagated throughout 
the metal. The oxide formed has a much lower melting-point than 
that of the metal, and is detached, leaving the iron continually bare. 

Highly carbonised steels, whose melting-points are appreciably 
lower than that of iron and in the neighbourhood of the oxide of the 
metal, do not lend themselves to cutting because the oxidation does 
not propagate itself; nor does cast iron, on account of the impossi- 
bility of eliminating the oxide mixed with the molten metal. Iron 
and steel are about the only metals that can be cut by the pxy- 



/ 



138 MODERN METHODS OF WELDING 

acetylene process. This is owing to the oxide of iron and steel 
melting at a much lower temperature than the metal itself. Other 
metals, where the melting-point of the oxides and the metals are 
nearly equal to one another, cannot be cut by this process. The 
reason why iron and steel can be cut is because, when the metal is 
heated to redness, and oxygen impinges upon it, it is immediately 
oxidised, and the pressure of the oxygen blows the oxide away as it is 
formed, leaving a clean cut through the metal. Most of the non- 
ferrous metals cannot be cut by oxygen for the reason stated above, 
and also very high carbon steels do not lend themselves easily to 
cutting. They can be cut, but it is very difficult, and many failures 
occur. Nor does cast iron lend itself to cutting with an oxy-acetylene 
cutter. 

Cutting by a jet of oxygen can only be applied to iron and steel 
in a continuous manner by contact with oxygen, for the reason 
that iron and steel oxidise very rapidly when heated to redness, and 
the oxide of iron formed by the impinging of the jet of oxygen com- 
bines and forms in a molten mass on the steel or iron plate; and, at 
the same time that the molten oxide is formed, the pressure of the 
oxygen blows the molten mass away, leaving a clear channel through 
the whole thickness of the plate. In order to make the cut continu- 
ous, it is necessary to maintain the steel plate at a red heat along the 
line of cutting. Taking into consideration that the plate absorbs 
a quantity of the heat by conducting it over the cold parts of the 
plate, the cutting pipe has to have a preheating flame, in addition to 
the jet of oxygen for blowing away the oxide as it is formed. 
The cutting pipe must be regulated for speed by the heating 
of the plate, and this heating must be continued as the cutting pro- 
ceeds. It is not necessary to heat the plates to more than red heat 
if a clean cut is desired. By raising the temperature to a welding 
heat, cutting action is stopped, and the metal becomes blobbed and 
forms a clot of oxide on the top of the plate. 

One must try to reduce the oxygen to a minimum by regulating 
the supply. It is not necessary to have high pressure or a large 
nozzle, except when cutting very thick stuff, because excess of 
oxygen means that the oxide will contain an excess of oxygen and 
the resulting oxide will be Fe 3 4 — i.e., three of iron and four of 
oxygen. If the oxygen is correctly regulated and the pressure not 
too heavy, the cutting will be much more economical, and more 
lineal feet will result, with cleaner cuts. The oxide formed would 
be FeO — i.e., one of iron and one of oxygen. The pressure of oxygen 
required to cut the various thicknesses must be carefully considered. 






CUTTING IRON AND STEEL 



139 



In many cases it is very indeterminate. What is desirable is the 
thinnest possible jet, with great length, capable of blowing the oxide 
away as it is formed, leaving the narrowest clean cut, and using 
oxygen at the very lowest pressure. The heating flame — its intensity 
and length, the distribution of heat— always influences the result, 
and its direction and distance are most important. 

Also, the purity of the oxygen is most important. At 99 per 
cent, purity, the maximum lineal feet of cutting can be obtained; 
95 to 96 per cent, of purity reduces the lineal cutting from 10 to 
15 per cent. With 90 per cent, cutting will only be intermittent. 




Fig. 70. — The Radiograph Cutting Steel Plate with the Oxy-Acetylene 
Flame, at Speeds Varying from 18 Inches to 2 Inches per Minute on 
Plate from i Inch to 20 Inches Thick. 



It will be noted that practically any thickness can be cut, from the 
thinnest to 16 or even 20 inches thick. With thick plates machines 
are needed to guide the line of cutting. Fig. 70 illustrates cutting 
a large plate. 

Where cutting has to be done by hand, care must be taken that 
the line of cutting is straight. In many cases, rollers are used to 
steady the cutter and to act as a guiding support. Operators 
must see that the heating flame and the delivery of the oxygen for 
cutting are regulated proportionally to the thickness of the plate to 
be cut. The pressure should be regulated at the reducing valve, 
and the minimum pressure must be used in all cutting operations, 
as a cleaner cut will be got. If a high pressure of oxygen is used 



140 



MODERN METHODS OF WELDING 



when cutting iron or steel, it spreads around the place where heating 
is taking place; hence it cools the surface, thereby retarding the 
cutting. 

It is not necessary to have increased pressure of oxygen. Many 
welders think that the higher the oxygen pressure, the quicker 
and better. This is a fallacy. Pressures from 10 to 40 pounds are 




Fig. 71. — Coupled Cylinders, for Continuous Work. 

ample for most commercial thicknesses, and more cutting and neater 
work will be obtained if the oxygen is kept at these pressures. 
Further, the saving in oxygen is large — quite 20 per cent. It is' not 
pressure that is needed, but volume. When cutting a great thick- 
ness, several cylinders are brought into requisition and coupled up 
together. From this one gets a large volume; but it only needs a 
medium pressure. The above illustration shows these coupled by 
cylinders. 



CUTTING IRON AND STEEL 



141 



This arrangement enables three cylinders at a time to be de- 
tached when empty, and replaced with full ones, while any or all 
of the others are feeding oxygen to the regulator fixed on the tripod 
stand in the centre. 




00 £ 



O £ 



& < 



Hi # 

Q S 

^ s 



Manufacturers should use the oxy-acetylene cutting process 
much more than they do at the present time. They will find impor- 
tant advantages through operating the torches mechanically, when 
such a procedure is practicable. More notable among the benefits 
secured from mechanical control are increased production from the 



142 



MODERN METHODS OF WELDING 



cutters and greater uniformity of work. Experience is required to 
enable the hand operator of a cutter to produce uniform cuts. In 
shops, the use of mechanically operated cutters eliminates the 
personal equation and generally improves the quality of the 
work. 

Figs. 72, 73, and 74 are remarkable and wonderful machines. 
You will note the ease with which the cutter is handled, also 
the clea,n-cut edge which it leaves, thereby saving machining. 




Fig. 73. — Circular Cuts in Steel Plate 2\ Inches Thick, with the Radio- 
graph, at a Speed of 6 Lineal Inches per Minute. 

Inside and outside diameters of these flue sheets for special heaters were cut with 
the Radiograph and the oxy-acetylene torch. 



It is also the means of increasing production, as cutters are moved 
at the correct rate, which is predetermined by the feed mechanism. 

Various mechanically operated equipments are designed for 
particular requirements. There are also standard designs of mechan- 
ical cutters and welding blowpipes, which are being used with great 
success. Provision can be made for the mechanical control of cutters 
adapted for use on parts of a variety of different shapes. 

The three illustrations show that, in addition to making straight 
cuts on flat plates, it is quite feasible for cutters to follow irregular 



CUTTING IRON AND STEEL 143 

outlines on flat plates, or to make cuts on cylindrically shaped 
pieces. 

With many of these mechanical equipments, the cutters are 
guided in such a way that they follow the line upon which it is 
desired to make a cut without calling for special attention from the 
operator. As previously mentioned, the provision of power drive 
sets the pace of the cutter, so that it is fed to the work at a prede- 
termined speed suitable for the thickness of the metal that is being 
cut. Figs. 72 and 73 show two mechanically worked cutters for 
cutting ragged edges for such pieces as boiler heads, which have 
a flange drawn up around the circumference. In Eig. 72 the 
cutter is shown trimming the flange off a boiler front which is made 
of steel plate 1| inches thick. It will be apparent from the illus- 
tration that the cutter is supported by a head carried on a radial 
arm, on a machine which is so designed that the cutter head can be 
traversed in either direction on the radial arm, and this arm can be 
swung round the column of the machine. This combination of 
movement enables the cutter to be fed round the edge of cylindri- 
cally shaped pieces, as shown. The cutter head is furnished with 
the wheels, which engage both inside and outside of the work to 
provide for holding the point of the cutter in proper relation to the 
plate it is cutting. The cutter head is worked by the electric motor 
seen above the radial arm, which transmits power to the wheels on 
the head, so that they serve the double purpose of holding the cutter 
in the proper position, and feeding it over the work at the proper 
rate. The plate being 1J inches thick, it cuts at a rate of 1 foot per 
minute, and leaves a sufficiently good finish, so that no subsequent 
machining operation is required. The Radiograph is a portable, 
motor-driven machine, combining carriage and driving mechanism 
with motor attached, oxy-acetylene or oxy-hydrogen cutting torch, 
and means for guiding the heating or cutting gases along straight 
or curved lines, at constant speed adjusted according to the thick 
ness of the plate and size of the tip used. 

In making motors for steam turbines, the New York Shipbuilding 
Corporation pour the molten steel into the mould, which is made so 
that the rotor casting stands on end, makes the casting longer, 
which acts as a riser, that applies pressure and assists in production 
of a solid casting. Obviously, it is necessary to cut off this surplus : 
and during the process of machining this steel casting is set up in 
a lathe. Supported in this way, it is an easy matter to rotate the 
casting at a suitable speed, so that a cutting blowpipe supported in 
the proper relation to the work will have the steel casting fed to 
the cutter, at the proper rate for making this cut. 



144 



MODERN METHODS OF WELDING 



The illustration below is the casting described herewith. You see 
that it is in the lathe, and cut through ; the blowpipe is fixed over 
the casting. 

This rotor casting is 9 inches thick by 16 feet 6 inches in circum- 
ference, and the cut was completed by the oxy-acetylene cutter in 
the remarkably short time of thirty -five 'and a half minutes. A 
good idea of the quality of the finished surface left by the cutter 
will be gathered from the illustration. 




Fig. 74. — Body of Steam Turbine Rotok oe Cast Steel. 

The end is being cut off by rotating it in the lathe to feed it to the flame of the 
cutting torch. It is 9 inches thick. 



Users of cutting and welding blowpipes should make themselves 
familiar with the properties of both hydrogen and acetylene; but 
there are some who have not had occasion to investigate the proper- 
ties of carbo-hydrogen. This gas contains from 85 to 88 per cent, 
hydrogen, and 15 to 12 per cent, of light hydrocarbons of the higher 
heating series. It is claimed that less oxygen is required for the 
combustion of this gas than for either acetylene or hydrogen; and 
the temperature of the carbo-hydrogen flame is approximately 
4,800° F. 

In referring to the properties of combustible gases which make 



CUTTING IRON AND STEEL 145 

them suitable for use in cutting and welding, confusion frequently 
arises through a misconception of the relation which exists between 
the number of heat units per cubic foot of gas and the temperature 
which can be developed by the combustion of that gas. For the 
performance of the cutting and welding operations, the number 
of heat units per cubic foot of gas is a matter of minor importance 
in determining ability to give efficient service. It is the rapidity 
with which this heat is liberated to develop a high temperature which 
determines the suitability of the gas for use in the blowpipe. 

The fact is well brought out by comparing the heat value of carbo- 
hydrogen with that of ordinary illuminating gas, the former having 
approximately 480 British thermal units of heat per cubic foot, 
while the latter has approximately 600 per foot. Despite this 
fact, illuminating gas is unsuitable for use in a blowpipe, because, 
although it has 25 per cent, more available heat per unit volume of 
gas, this heat is not liberated rapidly enough to generate a tempera- 
ture suitable for the cutting of metals. 

It is claimed by the Carbo-Hydrogen Company that this gas has 
readily cut armour plate up to 24 inches thickness, using standard 
apparatus, and that open-hearth steel pit castings 36 inches thick 
across have been cut in half by a special apparatus, using carbo- 
hydrogen as the combustible gas. For this work a number of 
oxygen cylinders were manifolded together and a preheating flame 
was used, which was provided by a blowpipe fitted with a J-inch 
gas pipe, taking oxygen from the manifold supply direct. Of course, 
this was an unusual operation, and the cut was not made by one 
continuous traverse of the cutter. In the case of the 24-inch armour 
plate this was made in one operation. The composition of the carbo- 
hydrogen gas is such that an accurate, clean cut is made, and the slag 
produced is almost pure oxide of iron, there being very little pure 
iron in it. This indicates that the cutting is accomplished by a 
complete process of oxidation, which is the ideal method, and not 
by melting the iron. Where metal is severed by melting it is almost 
inevitable that a ragged surface should be left in making a cut, so 
that it is necessary to employ some subsequent process of finishing 
before the work is ready for use. 

In this chapter information has been presented concerning miscel- 
laneous applications which have been made of mechanically operated 
cutting and welding blowpipes, and attention has been called to 
the benefits secured through the substitution of mechanical con- 
trol of hand operations. Despite the increased production and 
higher quality of the workmanship secured through mechanical 

10 



146 



MODERN METHODS OF WELDING 



operations, many manufacturers are continuing to use cutters moved 
over the work by hand. There is no denying that the latter method 
is capable of producing highly satisfactory results when the cutters 
are placed in the hands of skilled operators ; but the average mechanic 
will frequently fail to produce good work until he has had some con- 
siderable amount of experience. 

It is well worth while for the manufacturer who has use for the 




Fig. 75. — Felling a Stack with an Oxygen Cutter. 



oxy-acetylene torch to investigate carefully the requirements of his 
work, with the idea of determining whether it could not be handled 
by one of the standard cutting or welding machines. 

If investigation shows that the work could not be handled on any 
of the available commercial equipments, the next step is to ascertain 
whether a special machine using standard cutters could not be deve- 
loped at a reasonable expense. If so, development of such an equip- 
ment will usually prove a highly profitable investment, both from 



CUTTING IRON AND STEEL 



147 



the standpoint of direct earnings and also by making an improve- 
ment in the quality of workmanship where cutting or welding opera- 
tions have to be performed. 




Fig. 75 shows an unique application of the cutting blowpipe, the 
stack cut through at the bottom at an angle to set the fall. 

Remarkable results, which have revolutionised many methods of 



148 MODERN METHODS OF WELDING 

steel cutting, are being obtained with motor-driven machines. 
One such machine is sold under the name of " oxygraph." By 
following a drawing with a motor-driven tracer, steel to the thickness 
of several inches is cut out accurately .in intricate forms. The 
motor is very small and compact and requires very little power. 
It can be driven either by battery or by wire attached to an electric- 
light fixture. Being motor-driven it moves with a uniform speed, 
and corners and curves are cut with great exactness. 

It will cut steel plate from 1 to 15 inches or more in thickness, 
it cuts with a narrow smooth kerf, along straight lines, sharp 
angles, or curves, according to the drawing or pattern. The panta- 




Fig. 77- — Tracer Wheel, Swivel Standard, Rheostat and Electric Motor 
with Speed Controller of No. 1a Oxygraph. 

graph principle is employed with a motor-propelled tracing wheel, 
with which the lines of the drawing are followed and reproduced with 
the cutting torch. The only power required is for revolving the 
tracing wheel, and this is supplied by a small motor attached to the 
tracing head, which may be connected to the ordinary electric light 
or power circuit. The speed of the cutting varies from 2 to 18 inches 
per minute. 

Machine torches of great power have been developed for oxy- 
acetylene and oxy-hydrogen cutting with the oxygraph that operate 
successfully on the heaviest work. The adjustment of the cutting 
flame is easily learned and skill in the operation of the machine 



CUTTING IRON AND STEEL 



149 



is soon acquired by inexperienced operators. An operator capable 
of running a drilling machine should be able to work the oxygraph 
efficiently after a few days' instruction. 

The oxygraph has wide application and many uses in tool shops, 
manufacturing plants, locomotive works, shipyards, drop-forging 
concerns, and wherever tools, dies, forgings, and shapes are produced. 
The cutting action of the torch flame is smooth and rapid, and as any 




Fig. 78. 



-Machine Cutting Torch with Motor Control Switch, and Rack- 
and-Pinion Vertical Adjustment. 



shape can be cut it is comparable to a metal bandsaw of great power, 
capable of cutting steel 15 inches thick at the rate of 4 or 5 inches 
per minute, following straight lines, curves, and angles, acute or 
obtuse. Thin sections are cut more rapidly, of course. 

Punches, dies, stripper plates, and bolsters are cut in tool shops 
with the oxygraph with resultant saving of time and cost, reaching 
to 500 per cent., and even more, saving in some cases 



150 



MODERN METHODS OF WELDING 



The usual practice in making a cutting or trimming die is to plane 
the block on the top and bottom, bevel the sides, lay out and drill 
holes to the line, cut out the walls between the drilled holes with a 




Fig. 79. 



-Small Solid End Connecting-Rod and Billet from which it was 
Cut on the No. 1a Oxygraph. 



broach or drift, and finish with a hammer, chisel, and file, or by back- 
ing out on a shaper or slotter. Almost invariably a die made in this 
manner warps and twists in the process, and requires either re- 




Fig. 80.- 



-Leather-Ctjtting Punch for Shoe Manufacture and Tool Steel 
Piece from which it was Cut. 



planing on the bottom or shimming up in the bolster. The removal 
of the mass of steel in the centre of the die relieves internal stress 
and lets the block warp out of shape. Not so when the rough die 
block is cut out with the oxygraph. All troubles of this sort are 



CUTTING IRON AND STEEL 



151 



eliminated and the danger of cracking in hardening is reduced to a 
minimum. The rough die block is preheated and cut before planing, 
using a paper drawing to guide the tracer wheel. When the open- 
ing has been cut, the die, still hot, is placed in an annealing box, 
covered, and left to cool. When cold it is planed and finished in the 
usual manner with the assurance that internal strains have been 
relieved. Finishing the die to precise dimensions and backing out 
for clearance is done in the usual manner. 

Not only is the oxygraph useful for blocking out dies but it may 
be used also to cut the stripper plates and bolsters. The use of the 
No. 1a oxygraph in a tool shop outlined in the foregoing is one of 
the many that can be made in the manufacturing plant. It may be 




Fig. 81. — Drop Forged Wrench Trimming Die Roughed out on No. 1a Oxy- 
graph and Ready to be " Backed Out." 

used for cutting metal templates, cams, patterns, risers for fire 
escapes, and all shape cutting of any description which comes within 
the range and capacity of the machine. 

The No. 2 oxygraph is designed for such work as cutting the side 
frames of mine locomotives, tadpole ends of rudder wings, crank- 
cheeks of marine engines, mast bands for ships, connecting-rods for 
locomotive and marine engines, locomotive valve motion links, 
eccentric rods, and hundreds of parts whose production by other 
means is slow and costly. 

Figs. 79, 80, and 81 show a few samples of what is possible 
with these wonderful small machines; those shown are by the 
oxygraph. 

The above and other illustrations following will serve to give 



152 



MODERN METHODS OF WELDING 



some range of work and the speed of performance. But no matter 
what the shape is, provided the metal is steel or wrought iron 




^Vw^^ 



No. 1 




No. 1 



No. 1 






No. 3 



w 




No. 3 



Fig. 82. — Views of Three Sets op Dies Cut from 110-Point Carbon Steel, 
2J Inches Thick, on No. 1 Oxygraph. 

which may be forged to shape, it doubtless can be advantageously 
cut in the process of fabrication to reduce forging and machining 
cost. Forge shops use the oxygraph to increase the productive 



CUTTING IRON AND STEEL 



153 



capacity of their forging hammers and presses. For instance, a 
billet weighing many tons may be forged to a roughly rectangular 
shape, and from that be cut in two, three, or four crank- cheeks 
weighing, perhaps, 2 tons each. The resultant scrap, in some cases, 
is of a shape that can be utilised for smaller work by being reforged, 
hence saving not only time in forging and machining, but metal as 
well. Cutting may be started at the edge or within the edge of a 
piece, if conditions require it. The oxygraph torch flame quickly 
perforates, and thus the cost of drilling and handling is saved. The 
edges of the cut pieces are square and smooth and, in many cases, 
no machining is required for finish. If extreme accuracy is required, 
the cutting can be done so close to the line that machining is a light 
finishing operation only. These cutting machines are manufactured 
in America by Davis-Bournonville Company. 
The following are the costs : 



No. 


Time. 
Minutes. 


Oxygen. 
Cubic Feet. 


Acetylene. 
Cubic Feet. 


Length 
of Cut. 
Inches. 


Gas Cost 

at Id. Cubic 

Foot. 

Pence. 


1 

2 

3 


3-5 

4-0 
4-0 

11-5 


10-5 
13-2 
13-2 

36-9 


1-2 

1-4 
1-4 

4-0 


30 
34 
34 

98 


15 
17 

17 

49 



CHAPTER XXIV 
THERMIT WELDING 

Thermit Process. — This process of welding metals is effected by 
pouring superheated thermit steel around the parts to be united. 
Thermit is a mixture of finely divided aluminium and oxide. This 
mixture is placed in a crucible, and the steel is produced by igniting 
the thermit in one spot by means of a special powder, which gener- 
ates the intense heat necessary to start the chemical reaction. When 
the reaction is once started it continues throughout the whole mass, 
the oxygen of the iron being taken up by the aluminium (which has 
a strong affinity for it), producing aluminium oxide (or slag) and 




Fig. 83. — The Above is a Thermit Weld, in which New Teeth have been 

Welded in. 



superheated thermit steel. Ordinarily, the reaction requires from 
thirty-five seconds to one minute, depending upon the amount of 
thermit used. As soon as it ceases, the steel sinks to the bottom 
of the crucible, and is tapped into a mould surrounding the parts to 
be welded. As the temperature of the steel is about 5,400° F. it 
fuses and amalgamates with the broken sections, thus forming a 
homogeneous weld. 

It is necessary to preheat the sections to be welded before pour- 
ing to prevent the chilling of the steel. The principal steps of the 
operation are : to clean the sections to be welded ; to remove enough 
metal at the fracture to provide for a free flow of thermit steel ; to 
align the broken members and surround them with a mould to retain 

154 



THERMIT WELDING 



155 



the steel ; to preheat by a torch or other suitable heater to prevent 
chilling the steel; to ignite the thermit and tap the molten steel 
into the mould. 

This process is specially applicable to the welding of large sections. 
It has been extensively used for welding locomotive frames, broken 
motor castings, rudders and sternposts of ships, crankshafts, spokes 
of driving wheels, connecting-rods, and heavy repair work in general. 
One great advantage of the thermit process is that broken parts can 
usually be welded in place. For example, locomotive frames are 
welded by simply removing parts that would interfere with the appli- 
cation of a suitable mould. Thermit is also used for pipe welding 
and in foundry practice to prevent the " piping " of ingots. 




Fig. 84. — Thermit- Welded Crosshead. 



Preparation. — The first step in the operation of thermit welding 
is to clean the fractured parts and cut away enough metal to ensure 
an unobstructed flow of the molten thermit. The oxy-acetylene 
cutting blowpipe is very efficient for this operation. The amount 
that should be cut away depends upon the size of the work. Assum- 
ing that a locomotive frame is to be welded, the space should be 
about £ inch wide for a small frame, and 1 inch wide for a large 
frame. The frame sections are then jacked apart about f inch to 
allow for contraction of the weld when cooling. Trammel marks 
are scribed on each side of the fracture to show the normal length. 
If the weld is to be made on one member of a double-bar frame, 
the other parallel member should be heated with a blowpipe to 
equalise the expansion in both sections and prevent unequal 
strains. 

Fig. 84 shows a Thermit-Welded Crosshead, which was broken 



156 MODERN METHODS OF WELDING 

through the middle before welding took place. The two pieces of the 
crosshead, before welding, are bevelled on each edge of the fracture, 
so as to give a further area of thermit, thereby getting greater 
strength in the weld. The bevelling was done with an oxy-acetylene 
cutter, using acetylene and oxygen. 

Mould for Thermit W elding '.—The mould surrounding the frac- 
tured part should be so arranged that the molten thermit will run 
through the gate to the lowest part of the mould and rise through 
and around the parts to be welded. The thermit steel is poured 
through the gate and forms a riser which rises into a space after 
passing round and between the ends of the fractured crosshead. 
The thickest part is directly over the fracture, and the band overlaps 
the edges of the fracture by at least one inch. An opening is also 
made for preheating the ends to be welded. 

Patterns for the riser, pourings, and heating gates can be made 
of wood. The riser should be quite large enough, because the steel 
that first enters the mould is chilled somewhat by coming in con- 
tact with the metal even when preheated. This chilling effect is 
overcome by using enough thermit steel to force the chilled portion 
into the riser and replacing it by metal which has practically the 
full temperature received during reaction. When the mould and 
the box are filled and tamped, the wooden runner and riser patterns 
are withdrawn. The mould is then ready for the preheating and 
the drying operation, which causes the wax matrix to melt and run 
out. The mould must be made of some refractory material, owing 
to the intense heat. 

Thermit welding was first introduced in 1903 and was adopted 
on marine work, which has had a great many successful welds of this 
nature. It is being used largely by railway and tramway companies. 
One can, nearly always, see the process being worked in the streets 
on the tramway lines. 

There are many technical schools in every large city, where in- 
struction and practice are given in thermit welding, as well as other 
welding processes. 

Thermit Required for Welding.- — The quantity of thermit re- 
quired for making a weld can be determined from the cubic content 
of the weld. Calculate the contents of the weld and its reinforce- 
ment in cubic inches, double this amount to allow for filling the gate 
and riser, and multiply by 0-56 to get the number of pounds of 
thermit required. When wax is used for filling, the weight of the 
thermit can be determined as follows : Weigh the wax supply before 
and after filling the fracture. The difference in weight (in pounds) of 



THERMIT WELDING 157 

the quantity used multiplied by 22 will give the weight of thermit 
in pounds. 

When a quantity of more than 10 pounds of thermit is to be used, 
add 10 per cent, of steel punchings (not over J inch diameter), or 
steel scrap, free from grease, to the thermit powder. If the thermit 
exceeds 50 pounds, 15 per cent, of small mild steel rivets may be 
mixed with it. One per cent, by weight of pure manganese and 
1 per cent, of nickel thermit should be added to increase the strength 
of the thermit steel. 

Preheating — Making a Weld. — The ends to be welded should be 
red-hot at the moment the thermit steel is tapped into the mould. 
This preheating is done preferably by a gasolene compressed air 
burner. As previously mentioned, it melts the wax matrix used for 
filling the fractures to form the pattern for the reinforcing band. 
When the ends have been heated red, quickly remove the burner and 
plug the preheating hole with a dry sand core, backing it up with a 
few shovelfuls of sand, well packed. The end of the cone-shaped 
crucible should be directly over the pouring gate and not more than 
4 inches above it. To start reaction, place J teaspoonful of ignition 
powder on the top of the thermit and ignite with a storm-match. 
It is important that sufficient time be allowed for the completion of 
the thermit reaction and for the fusion of the steel punchings which 
have been mixed with the thermit. 

With charges containing from 30 to 40 pounds of thermit, the 
crucible should not be tapped in less than thirty-five seconds; 
with charges containing 50 to 75 pounds, forty seconds; 75 to 100 
pounds, fifty seconds to one minute. When welding a broken 
frame, as shown previously, the screw jack used for forcing apart 
should be turned back somewhat to relieve the pressure gradually 
as the weld cools. After pouring the mould should remain in place 
as long as possible (preferably ten to twelve hours) to anneal the 
steel in the weld; and, in any case, it should not be disturbed at 
least two hours after pouring. When welding a broken spoke in a 
driving wheel or a similar part, it is necessary to preheat the adjacent 
spokes in order to prevent undue strains through expansion and 
contraction. If a section of a spoke is broken out, it can be cast in, 
but if the space is over 6 inches long it is better to insert a piece of 
steel and make a weld at each end. Owing to the high temperature 
(5,400° F.), and the violent ebullition of thermit during reaction, 
the crucible must be relined with a very refractory material. The 
crucibles used for this purpose have sheet-iron shell and are lined 
with magnesia. 



158 



MODERN METHODS OF WELDING 



Filling Shrinkage Holes and Surface Flaws. — The filling of surface 
flaws in castings and forgings usually requires from 2 to 10 pounds of 
thermit. 

To make a weld of this kind, place an open mould around the 
part to be filled large enough to overlap it about § inch ; clean the 
hole thoroughly and heat to red-heat by means of a strong blow- 
burner. Use 18 ounces of thermit for each cubic inch of space, 




Fig. 85. — Thermit- Welded Rock Crusher. 



but not less than 2 pounds for any one weld. Place a small amount 
of thermit in the crucible, which, in this case, is of a small size for 
hand use. Ignite the thermit with the ignition powder, and as 
soon as it begins to turn add the remainder, feeding it fast enough 
to keep the combustion going. When the reaction is completed 
quickly pour the slag (which is about three-fourths of the liquid) 
into dry sand. Then pour the steel into the open mould and sprinkle 



THERMIT WELDING 159 

loose thermit on the top to prolong the reaction, as the casting, even 
when preheated, will have a chilling effect on the steel. 

Composition of Thermit Steel. — An average analysis of thermit 
steel is as follows: Carbon, 0-05 to 0-10; manganese, 0-08 to 0-10; 
silicon, 0-04 to 0-05; aluminium, 0-07 to 0-18 per cent. The tensile 
strength is about 65,000 pounds per square inch. 

Fig. 85 is a remarkable weld of a rock crusher for the Casparis 
Stone Company. The eccentric bearing broke off, leaving a 
fractured surface extending longitudinally through the bearing, 
measuring 6 feet 2 inches long and an average of about 7 inches 
thick. A mechanical repair was first attempted on the new brake, 
which, however, failed only after a few days' service. Resort was 
then made to the thermit process, and the casting was shipped 
to the thermit factory. The broken sections were lined up, a gap 
of about 3 inches between the sections was cut out with the oxy- 
acetylene flame, 90 pounds of wax applied in the welding gap, and 
a mould box built round the fracture. Six preheating gates were 
made in the mould. The preheating was begun at 4 a.m. on the day 
of the pour; 1|- hours of preheating were required to burn all the 
wax out of the mould. The preheating was kept up for about twelve 
hours until 3.45 p.m., the time the reaction started. The weld is 
illustrated on p. 158. 

Particular interest attaches to this repair because an extra large 
crucible, having a capacity of 2,000 pounds of thermit, and of some- 
what different design from the standard crucible, was used experi- 
mentally. The crucible was filled almost to its 2,000 pounds 
capacity, 1,750 pounds of railroad thermit being used. In spite of 
the enormous amount of thermit formed in one crucible, the re- 
action and pour were accomplished Avith entire success. The crucible 
rested steadily and motionless on its four supports throughout the 
reaction. Sixty seconds were allowed for the reaction to take place, 
after which the crucible was tapped in the usual manner, in the case 
of large welds by means of a long iron rod. From the moment of 
tapping it took two and three-quarter minutes for the contents to 
run out, as compared with the one minute generally required in the 
case of number 10 crucible. The illustration is self-explanatory. 
It shows the arrangement of the gates and riser, and indicates the 
excess of metal present after the mould box was finally removed. 



CHAPTER XXV 
PROPERTIES OF PRINCIPAL NON-FERROUS METALS 

Scattered throughout the pages of technical literature are various 
references to non-ferrous metals and alloys, the importance of which 
is apt to be lost sight of because they become inaccessible after a 
short time. It is therefore desirable that such information should be 
carefully sifted and what is useful in it collated and presented in a 
handy form. Such is the purport of the present chapter. 

The science of metallurgy has developed wonderfully within the 
last few years, especially with regard to the non-ferrous metals. 
Manufacturers are awakening to the fact that many of the disturbing 
influences which mar their best efforts are due to prevalent miscon- 
ceptions respecting the combined chemical compositions and the 
physical structures of the materials, and that henceforward science 
and practice must go hand in hand if true progress is to be attained. 

An ordinary chemical analysis, supplemented by the usual 
physical tests, was, at one time, considered to give the total history 
of an alloy. Things have changed, however, and it is now recognised 
that metals and compounds may be incorporated in an alloy under 
conditions which would so change the arrangements of the con- 
stituents as to render it difficult, if not impossible, to determine 
the original state of combination or the ultimate condition of the 
product. There has been no lack of fanciful theories in regard to 
the segregation, crystallisation, and fatigue of metals, some of 
them based on insufficient data derived from purely physical 
and chemical tests. 

A new branch of metallurgical study has recently come into 
prominence under the name of "metallography " — that is, the micro- 
scopical examination of the structure of metals, which has already 
been the means of revealing the causes of many peculiarities of metals 
and their alloys and confirming other theories concerning them 
which used to be looked upon as parabolic. One of the most im- 
portant properties or changes which occur in alloys is that of liquida- 
tion, which was only proved by metallographic examination. 

When a solution fluid at ordinary temperature is allowed to cool 

160 



PROPERTIES OF PRINCIPAL NON-FERROUS METALS 161 

below its congealing-point, the process frequently takes place in such 
a manner that, as cooling progresses, certain constituents of the 
solution congeal first, whilst the solution still remaining liquid under- 
goes constant changes in composition until a certain point is reached, 
after which this solution also congeals. The solution congealing last 
is called the eutectic (most fluid) solution. On examination of the 
latter, it will be found that during cooling a disintegration of the 
constituents previously dissolved in one and another has taken place, 
and that the solution now forms only an intimate mixture of these 
constituents. 

Many alloys show a similar behaviour when cooling. If, for 
instance, a melted zinc-copper alloy containing more than 72 per 
cent, of zinc be allowed to cool, zinc crystals are first separated, 
while an alloy poorer in zinc still remains liquid. This separation 
of zinc is continued until the content of the zinc has been reduced 
to 72 per cent., which takes place when the temperature has fallen 
to 1,404° F. This is the eutectic point: a eutectic alloy which no 
longer separates any constituents but solidifies throughout at that 
temperature consists, therefore, of 72 parts of zinc and 28 parts of 
copper. In congealing it disintegrates, however, to an intimate 
mixture of its constituents which, on reheating, first dissolve again 
in one another, and with an increase of temperature gradually dis- 
solve the previously separated zinc. If, on the other hand, the alloy 
contains less than 72 per cent, of zinc and more than 28 per cent, 
of copper, copper is, in congealing, first separated till, at 1,404° F., 
the composition of the eutectic alloy has again been reached and 
then also congeals. 

Specific Gravity. — The specific gravity or density of alloys corre- 
sponds only in a few cases with that which would result by calcula- 
tion from the specific gravities of the constituents. The specific 
gravity should be calculated from the volumes and not from the 
weights. Dr. Ure gives the correct rule as follows : Multiply the sum 
of the weight into the products of the two specific gravity numbers 
for a numerator and multiply each specific gravity number into the 
weight of the other body, and add the products for a denominator. 
The quotient obtained by dividing the said numerator by the 
denominator is the computed mean specific gravity of the alloy. 
With regard to the influences exerted upon the strength of metal 
by alloying, the following general law may be laid down. By the 
absorption of a foreign body the strength of the metal is increased. 
It grows with the content of the foreign body until the latter has 
reached a certain proportion, which varies in individual cases. 

11 



162 



MODERN METHODS OF WELDING 



When this limit has been passed, the strength again decreases, fre- 
quently with great rapidity, provided that the body itself does not 
possess greater strength than the metal. • By the addition of a third 
metal to an alloy consisting of two metals, it is sometimes possible 
to bring about an additional increase in strength. 

Limit of Elasticity. — In alloying a metal the limit of elasticity 
increases steadily with the breaking strength, limit of elasticity, and 
breaking weight moving more closely together. The limit of elasti- 
city usually increases still further when, with the increase of the 
foreign body added, the highest degree of strength has already been 
attained, and a decrease in strength reappears. Limit of elasticity 
and strength sometimes finally converge. 



Mixtures of Alloys. 





Copper. 


Tin. 


Zinc. 




Bell-metal ! 78 


22 




Standard bell-metal 


Gun-metal 


90 


10 


— 


Ordnance castings 


Gun-metal 




88 


10 


— 


Steam chest pumps 


Gun-metal 




86 


14 


■ — 


Hard bearing metal 


Naval brass 




62 


1 


37 


Stanchions, tube plates 


Sheet brass 




70 


— 


30 


For sheet tubes 


Ordinary brass 




66f 


— 


33* 


General use 


Manganese bronze 




56 


0-9 


41 




Gun-metal ord. 




88 


8 


2 


General use 


Yellow brass 




85 


3 


15 


General plumbing work 








Iron. 




Phosphor-bronze 


89-5 


10 


0-5 


Heavy bearings 











Mdting-Points. 


Boiling -Points. 




Degrees C. 


Degrees G. 


Aluminium 


658-7 


1,800 


Copper 








1,803 


2,310 


Iron 








1,520 


2,450 


Tin 








231-9 


2,270 


Zinc 








419-4 


905-7 


Gun-metal 








995 


1,825 


Red brass 








970 


1,780 


Low-grade brass . . 








980 


1,795 


Bronze with zinc 








980 


1,795 


Cast yellow brass 








895 


1,645 


Naval brass 








855 


1,520 


Manganese bronze 








870 


1,600 



PROPERTIES OF PRINCIPAL NON-FERROUS METALS 163 

The purest metals possess the greatest flexibility. By alloying 
this property is diminished, and sometimes almost reduced to 
nothing. The melting temperature of metals is frequently lowered 
by alloying. Therefore it is essential that, when welding takes place 
upon non-ferrous metals, precautions must be taken not to add 
impure metals from the welding -rod into the welded portion. 
Also it is important that the metal article being welded and the 
welding-rod shall be one and the same material, plus ingredients to 
replace the element that is volatilised during welding. 



CHAPTER XXVI 
DELTA METALS 

The alloys known under the name of " delta metals " are a series 
of high-class engineering alloys, of which the first was placed on 
the market in 1885 by the eminent metallurgist, the late Alexander 
Dick. These metals have been greatly developed and comprise a 
whole group of different alloys. Hence there are naturally always 
welding repairs in these metals to be done. A description of their 
properties will enable the student to distinguish them from other 
metals and alloys, so that the treatment may be administered as 
required. 

It is obviously impossible to combine in one single alloy all the 
physical and chemical properties suited to a great variety of pur- 
poses. The different standard alloys vary in composition accord- 
ing to the purposes for which they are more particularly adapted. 

Some alloys possess in every degree the properties of malleability, 
strength, and resistance to corrosion; others are superior bearing 
metals. Some have particular qualifications for electrical purposes ; 
others for high-speed machining for brass-founder's work. One 
is called silver bronze, possessing a silver-white colour. 

Metal No. 1 : Strongest malleable bronze for high-tensile forgings, 
castings, and rods. 

Metal No. 2 : Silver bronze (improved nickel silver) rods, forgings, 
and castings. 

Metal No. 3 : Specially adapted for solid drawn tubes. 

Metal No. 4: (Various grades) malleable bronze, strong as steel, 
tough as wrought iron, highest resistance to corrosion, for castings, 
forgings, stampings, rods, sheet, wire, etc. 

Metal No. 5: Antifriction bronze for bearing castings. 

Metal No. 6: Improved gun-metal for castings of every descrip- 
tion. 

Metal No. 7: Bronze to resist high temperature, castings, forg- 
ings, stampings, rods, etc. 

Metals Nos. 8, 9, 9a: Various grades of white antifriction metals. 

Of the various alloys, the most used is No. 4. Its great strength, 

164 



DELTA METALS 165 

equalling that of steel, its elongation, its toughness, its malleability, 
and its property of resisting in a marked degree the corrosive action 
of sea and mine water, chemicals, gases, etc., render this particular 
brand the most useful for all classes of work in which durability, 
strength, and reliability are the qualities chiefly to be taken into 
consideration. It should be borne in mind that when objects made 
from different metals or alloys are, while in metallic contact with 
each other, immersed in sea water, brine, or any other exciting fluid, 
galvanic action will be set up, which will bring about deterioration 
or decomposition of the metals. The rapidity with which this 
deterioration takes place, and also the question of which of the metals 
is chiefly attacked, depends upon the relative position of the different 
metals in the electric scale. Metals hardly suffer at all when in con- 
tact with those which are electro-negative to them ; but when in 
contact with a metal which is electro-positive towards them they 
are rapidly destroyed. For this reason delta metal should never be 
placed in metallic contact with copper or gun-metal when immersed 
in sea water, or used in running machinery or other plant which is 
exposed to the action of corrosive fluids. 

From this it is clear that operators should take care in the weld- 
ing of delta-metal articles. A welding-rod must be used of the same 
constituents as the article being welded, plus the deoxidising sub- 
stance. The results of tests from this metal have shown it to have 
a tensile strength of 24 tons per square inch, elongation from 30 to 
40 per cent., and limit of elasticity 19-02 tons per square inch. 
When reheated to 550° C. (a dull red colour) it becomes soft, and 
is then one of the most malleable copper alloys in existence, as it is 
in a semiplastic state, in which it can be worked as easily as wrought 
iron, and can be stamped, forged, and pressed to any extent required. 
As these operations add 50 per cent, strength to the metal, without 
impairing any of its other valuable qualities, it is obvious that, for 
the majority of uses, the wrought material is to be preferred, the 
more so as it is free from defects which are sometimes found in 
castings, such as blowholes, etc. 

Forged bars of this alloy show, as a result of four tests, a tensile 
breaking strain of 34-4 tons per square inch, with an elongation of 
26-25 per cent. Its great strength is but little affected by increase 
of temperature. This quality adds considerably to its value for 
engineering purposes, such as engine fittings exposed to hot steam. 
The result of the test at a temperature of 506° F. was that it lost 
only about 17| per cent., while at 500° F. brass lost 38 per cent., 
phosphor-bronze about 31 per cent., and gun-metal 33 per cent. Delta 



166 MODERN METHODS OF WELDING 

metal can be roughly described as a copper-zinc alloy, chemically 
combined with definite proportions of iron and other elements. 
The secret lies, not only in the use of virgin metals in the exact pro- 
portions, but still more in the proper methods of combining these, 
and eliminating during the manufacturing processes certain other 
elements after these have produced the desired effect. 

The foregoing description is one which sets out the properties 
of a metal very largely used in many workshops. The author 
has not seen them detailed before; but he has had considerable 
experience in the welding of it, and articles made of it are now 
coming into various workshops or welding depots for repairs. 

Welding-Rods. 

Welding-rods for use with delta-metal articles should contain the 
same pure metal, and also a trace of phosphorus and aluminium. 
These are added to the metal to prevent oxidation. The welding-rod 
should be manufactured from pure metal, and the constituents or 
ingredients uniformly distributed through the mass. They should 
be made in sizes from ^ to \ inch diameter and 24 inches long. 
They are usually drawn down into wire of various thicknesses and 
stocked by the manufacturers. They should also be made in various 
grades to suit the articles to be welded. 

Preparation of Articles. 

The welding of delta metal is easy of application, as the metal 
is very pure. The area to be welded must be bevelled in the usual 
course. If it is not over § inch thick it is only necessary to bevel 
one side, but if over f inch thick it is necessary to bevel both sides. 
Afterwards the weld has to be thoroughly cleaned. This is very 
important, because the molten metal will not adhere to a greasy 
surface. 

Preheating. — The laws of expansion and contraction have neces- 
sarily to be considered in welding this metal. Therefore, it is desir- 
able always to preheat the articles, and, after welding sharply, they 
should be returned to an annealing furnace to heat up and allowed 
to cool slowly until quite cold. Apart from the question of expan- 
sion of the metal, preheating saves a good quantity of gases in 
welding. 

Blowpipe Tower. — The power of the blowpipe is, generally speak- 
ing, the same as for copper, or a size larger than that used for iron 
or steel. The regulation of the flame is very important. This must 



DELTA METALS 167 

be done with great accuracy, and there must be no excess of acety- 
lene or oxygen. The former would carbonise the weld, the latter 
would oxidise it. The oxygen pressure must not at all be increased 
over that stated by the makers. The flame should be regulated 
till a clear white jet or cone is perceived and kept at this until the 
blowpipe gets somewhat heated and the flame begins to get less, 
when a little more acetylene should be turned on to make the even 
cone. In no case should excess oxygen be turned on. 

Method of Welding. — The preheated and bevelled article should 
be on the welding table, the blowpipe regulated, and the weldinr- 
rod in the left hand. Approach the welding line at about \ inch 
from the edge, keeping the white top of the flame -£% inch from the 
metal. As the melting starts, the blowpipe should be passed over 
to the edge, and this melted. At this period the welding-rod should 
be nearly at the welding-point. As soon as the edge is melted, put 
a little from the welding-rod into the molten mass to fill up the 
bevel, and continue the movement of the blowpipe along the line 
of welding in a gyratory movement, advancing at the same time 
with the necessary addition of the welding-rod to fill up the spaces 
until there is enough metal added to fill up the bevel. The welding 
must be continuous when once started, and one must not go over 
the weld twice without adding additional welding-rod. The flux 
must be used along with the welding-rod, and dipped while hot into 
the flux jar. No more must be used than is necessary — just sufficient 
to clean the metal and prevent oxidation. When the weld has been 
completed, the welded article should be put back into the annealing 
furnace and heated to 550° C, then, when cold, the weld may be 
hammered. 

Failures. — These only occur through lack of metallurgical know- 
ledge: adding a rod of inferior quality; bad penetration; allowing 
the oxide to form internally in the metal, forming blowholes ; being 
too long on the weld, and causing the metal to become too liquid, 
burnt, and oxidised ; or melting the metal to its boiling-point instead 
of its melting-point. 

All these defects are easily overcome. They require a little 
practice and careful study of the metallurgical and technical points. 
With this knowledge failure is impossible. 



CHAPTER XXVII 
ALUMINIUM 

Aluminium has a silvery-white appearance, and is capable of taking 
a very high polish. It is one of the soft metals, its hardness being 
only about 2-5. Its most valuable property is its lightness, the 
specific gravity being 2-56, varying slightly with the impurities 
present. Rolling, hammering, and stamping increase its specific 
gravity somewhat, that of worked metal being as high as 2-7. 
The tensile strength of aluminium castings is about 6 or 7 tons per 
square inch in section, although wire may reach 15 to 30 tons> 
depending on its fineness. 

The elastic • limit is about 3 to 4 tons in the case of castings, 
and may be as high as 15 tons for wire. The metal flows readily 
under pressure, and is therefore both malleable and ductile. It can be 
rolled into very thin sheets or drawn into fine wire. Aluminium 
melts readily, its melting-point being 658° C, and its boiling-point 
is estimated at 1,800° C, being non- volatile in ordinary circum- 
stances. It has a very specific heat, about 0-308, which remains 
constant up to about 800° C. Its latent heat of fusion is given as 
100. It is a good conductor of electricity, the conducting power 
of pure aluminium (silver taken as 100) being about 56; but this 
should be modified by the presence of impurities, and by the condi- 
tion of the metal, whether annealed or not, owing to its lightness. 
For equal conductiveness the weight of the aluminium is about 
48-5 per cent, that of copper. It is used largely in the manu- 
facture of alloys and for many purposes, and is in big demand for 
motor-car castings, whilst its further use has been extended by 
the advent of the aeroplane. Owing to its low tensile strength, its 
usefulness has been curtailed for many engineering purposes. 
Hence many aluminium alloys have been brought out in the effort 
to combine strength with lightness. 

The lightness, low cost, and ease of working peculiar to sheet 
aluminium have combined to make it one of the most popular metals 
for the manufacture of various articles from the sheet form. The metal 
can be obtained in grades from dead soft to hard rolled. A square 

168 



ALUMINIUM 169 

foot of 14 S.W.G. sheet aluminium weighs 1-11 pounds, the same 
size copper weighs 3-70, and brass 3-56 pounds. The difference in 
prices for the same sizes is as follows : 

One square foot of sheet aluminium costs Is. 2Jd. 
„ copper „ 3s. 

,, ., ,, brass ,, 2s. 6d. 

Hence aluminium is much less than half the cost of other non- 
ferrous metals ; in sheet form it is undoubtedly (with the exception 
of iron) the cheapest material on the market. For this reason sheet 
aluminium has come into extended use for such work as motor 
body and railway coach construction, for ceilings and panels, 
and many other purposes. The welding of this sheet aluminium 
is spreading rapidly. Operators should devote much time to its 
study from a metallurgical point of view, so that when they come 
to weld it they may understand what takes place when the heat 
of the flame is used on the sheet and it becomes molten. 

Aluminium is without doubt the most difficult to weld of all 
metals. This is largely due to the difference in the fusibility of 
the aluminium oxide and aluminium metal. When two separate 
pieces of aluminium are welded together at their edges, by means of 
the welding flame, the melted parts do not flow properly together, 
as is the case with iron, where the melting-point of the oxide is lower 
than that of the metal. At high temperatures aluminium has great 
affinity for oxygen. The molten parts become covered, under the 
influence of the welding flame, with a fine coating of oxide, which has 
great power of resistance to the flame, and, on cooling, the parts 
remain unjoined. Therefore, if aluminium parts are to be welded 
together properly, this skin of oxide must in some way be destroyed. 
This can be done to some extent mechanically. The destruction of 
the covering of the oxide can be brought about by moving or puddling 
the molten metal of the weld by means of the aluminium wire used 
as a feeding-rod to let the separate drops, already formed, flow to one 
another. With this method, however, there is a danger that the 
weld will be a failure, not a homogeneous one. Almost certainly soma 
part or other of the oxide will remain in the weld, which would prob- 
ably make it defective. There are also many points to watch care- 
fully in the welding of aluminium. It is imperative that it be sup- 
ported on the underside of the weld. Otherwise, as soon as the 
melting takes place the molten metal would fall through, leaving a 
hole in the weld, which the student would find it difficult to fill up 
without causing further holes and burning the aluminium, causing 



170 MODERN METHODS OF WELDING 

even further oxidation. Mechanical puddling should not be prac- 
tised, because it is only a makeshift, which is seldom successful. 
Proper welding — that is, a homogeneous joint — can only be done 
by very careful study and practice. An important point is the 
use of a good flux, which will cause the oxide to melt or break 
down to the same temperature and at the same time as the metal 
itself. 

The difficulty will be seen when it is explained that the melting- 
point of metallic aluminium is 650° C, whilst the melting-point of 
aluminium oxide is 1,800° C. To produce a flux that will dissolve 
the oxide at the low melting-point of the metal, and at the same time 
protect the hot metal from contact with the air, is no easy problem 
to the chemist and metallurgist. It is only recently that such fluxes 
have become obtainable. These vary considerably in their elements 
and compositions. There are several at present being marketed. 
Each one pleads it is the best; some are good, but others are no use 
whatever. If a good flux is obtained, there should be no reason 
(after constant practice) why operators should not make very satis- 
factory welds in aluminium. Light hammering of the weld and 
reheating to a temperature of about 450° C. are beneficial. Alumin- 
ium welding is now quite an important branch of the oxy-acetylene 
welding industry, and is employed more particularly in connection 
with brewing, where aluminium is largely superseding enamelled 
ware. Fluxes should always be removed by washing off as the 
welding job is complete. 

It is very important to choose with care a correct blowpipe for 
the welding of aluminium sheeting. This must be a very light one, 
much lighter than for the same thickness of iron or steel: just 
half the power would be plenty. One must also be very careful 
to watch the oxygen pressure. This must be less than that specified 
by the makers, which is based on iron and steel. In all cases of 
welding pure aluminium it is imperative that the edges to be welded 
shall be absolutely clean, and the welding-rod of the purest metal 
obtainable, so as not to get impurities into the weld, which would 
cause it to be defective. 

Aluminium being of low melting-point, the operator requires 
great patience and skill when welding, and must avoid burning the 
metal, or getting much above its melting-point, as the heat spreads 
rapidly, especially on light work. 

If the metal melts too much on each side of the weld and makes 
too large a molten bath, the result is a rough and probably defec- 
tive weld. Therefore, neither the blowpipe nor the flame must be 



ALUMINIUM 



171 



large, and the oxygen pressure must be just sufficient to keep in the 
flame, which must have the smallest jet possible. 

The welding-rod for aluminium welding is usually made from 
pure aluminium drawn wire of diameters for the various thicknesses 
to be welded. These rods are usually kept in stock by various 
factors of acetylene equipment. 

It is imperative that the rods be pure, and free from even a 
trace of copper. Copper is very detrimental to welds and causes 
(in moisture or water) corrosion. In welding pure aluminium parts 
it is not always necessary to preheat, because in many cases the 






Fig. 86. — Fractured Aluminium Gear Case. 



aluminium article is able to stand the welding without preheating ; 
but hammering and annealing afterwards increase the strength of 
the weld greatly. If flux has been used, the article should be brushed 
in running water if possible, because the flux has a corroding effect 
on the metal. 

The above illustration shows a motor aluminium crank case 
which was welded successfully and afterwards annealed. A neat 
job was made and in no way distorted. 

In dealing with alloys the most important properties which are 
desired are strength and durability combined with ductility. Tests 
have been applied to commercial specimens of alloys upon the market. 



172 



MODERN METHODS OF WELDING 



Alloys which are lighter than aluminium itself generally contain 
magnesium, which reduces its tensile strength, and renders it 
brittle and less permanent than aluminium itself. An alloy con- 
taining approximately 76 per cent, of aluminium, 21 per cent, of 
zinc, 3 per cent, of copper, has an ultimate strength of 12 tons per 
square inch. This is a mixture from which motor crank cases are 
frequently made. 

Copper alone does not result in any great gain in beneficial proper- 
ties, as is seen by the fact that an alloy approximately 95 per cent . 
aluminium and 5 per cent, copper only reached a maximum ultimate 
stress of 8 tons per square inch. With the exception of duralumin, 
none of the commercial alloys investigated showed any remarkable 
excellence, or, indeed, bore out the claims of the makers. Indepen- 
dent investigation in the laboratory with alloys of definite com- 
position afforded interesting results which were exhaustively tabu- 
lated according to the method of mechanical and heat treatment. 
The result of annealing after treatment was invariably to lower the 
ultimate strength, while rolling had the opposite effect. 

Sand cast alloy containing 15 per cent, of zinc had an ultimate 
strength of 11-19 tons per square inch, but a rolled bar reached in 
one case to 17 tons, wire being 19 tons per square inch, even after 
annealing at 400° C. An alloy containing 20 per cent, zinc showed 
higher tensile strength all round, sand cast 17 tons per square inch, 
1 \ inch diameter rolled bar 22J tons per square inch. Copper alone 
in small quantities does not cause any appreciable improvement, 
but it can be advantageously used in conjunction with zinc. Experi- 
ments with aluminium- zinc alloys to which 3 per cent, of copper 
was added showed ultimate strength as follows : 



15 per cent. Zn 

20 

26 



Sand Cast. 



14-15 tons 
15-55 „ 

18-25 „ 



Chill Cast. 



14-9 tons 
14-2 
22-22 ,, 



Rolled Bar. 



23-6 tons 
23 

27-92 „ 



The effect of magnesium in small quantities is, on the other hand, 
most decided, and from 25 to 5 per cent, magnesium has resulted in 
an alloy which, in rolled condition, possesses an ultimate strength of 
28 tons per square inch. Light alloys are fairly permanent, if not 
exposed to high temperatures, although cases of deterioration have 
been known with alloys of approximately 80 per cent, zinc and 20 per 
cent, aluminium. The chief trouble is corrosion, which is marked in 



ALUMINIUM 173 

the case of alloys containing copper. Indeed, the corrosion of all light 
alloys is hastened by contact with copper or brass when immersed. 
The use of light alloys in constructional work often entails welding, 
etc., and great care should be exercised, as these alloys are generally 
very sensitive to all such treatment, which may thus lead to an un- 
expected failure. 

Certain aluminium alloys, generally known as duralumin, 
became materials of high importance during the war, and owe their 
great development to their mechanical properties. Some of these 
are singular and due apparently to method of tempering. Investi- 
gations were made with a duralumin of the following composition : 
Aluminium 93-9, magnesium 0-43, copper 3-7, manganese 0-Q, 
zinc 0-25, silicon 0-58, iron 0-53 per cent, (some of these minor con- 
stituents may probably be regarded as accidental). Following 
the ordinary practice, the metal was heated to 450° C, quenched in 
cold water, and left to itself. The quenching itself did not seem 
to change the properties of the alloy to any important extent, but 
the breaking strength, impact strength, elastic limit, and hardness 
increased afterwards, within a day or two, while the elongation and 
reduction in area were little affected. 

Aluminium alloy that is to be welded should be scraped and 
cleaned, and if the stock is more than \ inch thick the edges should 
be bevelled. If the blowpipe, when welding, appears too fierce 
a flame, then this must be reduced by (1) reduction of oxygen, and 
(2) an excess of acetylene. This excess of acetylene does not injure 
aluminium alloy, but lowers the flame temperature, which is desirable, 
owing to the low melting-point. 

Coal-gas, instead of acetylene, mixed with oxygen would do for 
welding aluminium, as it is a softer flame. Often good sound welds 
are made with these gases, and it is very easy to fix up to the town 
gas; one precaution must be taken — that is, the coal-gas must be 
passed through an hydraulic safety valve the same as acetylene; 
the coal-gas is under the same pressure as the acetylene, therefore 
it has to be used in the same way. Also acetylene and coal-gas may 
be used for the same service in welding aluminium. 

Before welding, articles of aluminium usually have to be heated 
up in the furnace to about 300° C, being covered with asbestos in the 
furnace. As soon as this temperature has been reached, the article 
should be drawn from the furnace, welded immediately, and, when 
completed, returned to the furnace to be reheated to 300° C, then 
allowed to cool till the next morning in the furnace, and kept free 
from air to prevent shrinkage, cracks, and fractures. Many alumin- 



80 


76 


70 


15 


20 


26 


2 


3 


4 



174 MODERN METHODS OF WELDING 

ium -alloy castings may be welded without preheating, such as lugs 
or projecting pieces broken off completely. There is a great variety 
of alloy mixtures, many of which are found in welding shops in 
articles such as gear cases, engine cases, chain cases from automobiles. 
It is hard to judge accurately the composition of these alloys. 

It is well to stock welding-rods of three different compositions, 
which should be as near as can be to the same analysis as the articles 
to be welded. From tests the author has made, the three following 
mixtures can be used, and will give successful results if the articles 
are graded to suit them : 

Aluminium 

Zinc 

Copper 

In welding aluminium-alloy articles, the rod must not be pure 
aluminium. It must be of the same materials as the article to be 
welded. When welding, a flux must be used the same as for welding 
pure aluminium. Aluminium alloy is not a ductile metal. Hence 
it must be treated as one treats cast iron, and the j)henomenon of 
expansion and contraction has to be dealt with. 

Fig. 87 is an alloy gear case, which plainly tells what parts are 
broken and have to be made good. There are three cracks between 
the cylinder openings. 

The first procedure on such a casting is to clean it thoroughly and 
free it from oil. Secondly, bevel the edges. Thirdly, prepare a 
piece of sheet iron and fix inside the case under the cracks. This 
must be larger than the cracks, to prevent the molten metal from 
falling through. This will enable you, too, to penetrate right through 
the weld. Having got this all prepared and placed on the welding 
table (whilst cold), and put just in the position where welding will 
take place, get the blowpipe, welding-rod, and flux all ready. Test 
the hydraulic safety valve. See that you have enough oxygen and 
acetylene. All being ready, and the tools at hand, place the article 
to be welded in the furnace, and let it remain there till a temperature 
of 350° C. is reached. Then remove from the furnace and place in 
the exact position as when cold, and immediately commence to 
weld. Then proceed regularly and progressively until the whole line 
of welding has been done, adding at the same time, as the progression 
takes place, equal amounts of the welding-rod to fill up level to the 
top of the edges, dipping the hot rod in the flux from time to time. 
The welding must be done quickly, and must not be gone over a 
second time. The tip of the flame must not be allowed to touch the 



ALUMINIUM 



175 



metal. Immediately the weld has been completed, it should at 
once be placed in the furnace again, and the temperature raised to 
325° C. Afterwards it must be allowed to cool slowly, free from 
any draughts or air. 

After cooling, the article should be examined to see if the weld 
has been homogeneous, and searched for any further cracks. There 
should not be any if the heating has been uniform. The weld should 
be cleaned up, or machined if required, and tested to see if it has 
been distorted in any way. If not, the weld is satisfactory. 

If operators will follow out the instructions above, they will 




Fig. 87. — Fractured Aluminium-Alloy Gear Case. 



succeed on every occasion. Each point must be watched, studied, 
practised, and practised time after time. 
The following are important : 

(1) Blowpipe must not be too powerful; oxygen at its minimum 
pressure; acetylene always slightly in excess. 

(2) Articles must be well prepared, and placed in the welding 
position before placing in the furnace. 

(3) Articles must be heated to a temperature of 350° C. before 
starting welding. 

(4) Articles must not be allowed to go below the temperature 
of 275° C. while welding. If they do, they must be put back in 
the furnace and reheated to 350° C. The welding may then be 
completed. 

(5) After welding, the article must be put into the annealing 
furnace, reheated to 350° C, and then allowed to cool slowly. 



176 MODERN METHODS OF WELDING 

(6) Welding-rods must be approximately of the analysis of the 
welded article, and must be free from impurities. 

The chief uses to which magnesium is put are, as an alloy with 
other metals, and for intense illuminations of short duration. When 
alloyed with aluminium containing one or more other metals, the 
crystallisation and other properties are modified. As a scavenging 
alloy, it clears up oxide of other alloys. Because of its intense avidity 
for both oxygen and nitrogen it is valuable in aluminium, nickel, 








Fig. 88. — Aluminium- Alloy Gear Case Repaired. 

copper, brass, etc., and in special steels. In aluminium castings, 
for instance, less than 2 per cent, of magnesium cleans the metal, and 
leaves from | to 1| per cent, in the casting, about doubling its tensile 
strength, quadrupling its resistance to shock and jar, and producing 
a much more easily machined metal. 

Fig. 88 is an aluminium gear case, which had one corner of the 
case broken, afterwards welded successfully. 



CHAPTER XXVIII 
COPPER 

Copper stands alone among the metals in having a reddish colour. 
It is capable of taking a high polish, but on exposure to the air the 
surface darkens considerably. It is comparatively soft (H=3), is 
easily scratched with a knife, flows readily under pressure, is both 
malleable and ductile, and can be rolled into thin sheets or drawn 
into fine wire, and readily worked into any form by stamping and 
spinning. 

It is malleable, both cold and at a red heat, but near the melting- 
point it becomes brittle. The tensile strength of cast copper is about 
13 tons per square inch, but rods may be obtained having a strength 
up to 26 tons, as mechanical working, especially wire drawing, greatly 
increases its strength. When copper is worked, it becomes hard, 
and loses its ductility to some extent. This can, however, be restored 
by annealing. The specific gravity of copper is from 8-8 to 9 (various 
figures are given by different authorities), depending on its state. 
Castings have a lower specific gravity than sheets, and the specific 
gravity of the latter is lower than that of wire. 

Copper melts at 1,083° C. and boils at 2,310° C. This is im- 
portant to remember as, if the heat in welding much exceeds the 
melting-point, the copper will be burnt and full of blowholes. 

It cannot be distilled. Its latent heat of fusion is about 44 
and its specific heat roughly 0-094 ; but this increases as the tempera- 
ture rises. The mean specific heat between 0° and 1° may be taken 
as 0-0939 to 0-00001778; the heat required to raise 1 gramme from 
0° to the melting-point and melt it would be 44+("094 x 1,085) = 
146 units. The coefficient of linear expansion is 0-00001596 for 
each degree centigrade rise of temperature. 

Copper is an excellent conductor of both heat and electricity. 
Its heat conductivity is 898, and its electric conductivity slightly less 
than that of silver ; taking the resistance of the latter as 1, that of 
annealed copper is about 1 -003, and that of hard drawn copper about 
1-086. It is necessary to say " about," because the electric con- 
ductivity is diminished very considerably by the slightest traces of 

177 12 



178 MODERN METHODS OF WELDING 

impurity. Copper can now be obtained so pure that the conducti- 
vity is considerably greater than that taken for pure copper when the 
standards in use were fixed. The resistance of a foot of pure copper 
wire, 0-001 inch in diameter, is 9-612 ohms. The conducting power, 
as in the case of all metals, falls as the temperature rises, the fall of 
conducting power being 29-3 per cent, for a rise of temperature 
from 0° to 100° C. 

The principal varieties of commercial copper are : ( 1 ) electrolytic ; 
(2) best selected (B.S.) tough. 

Electrolytic copper is prepared by electro-deposition from solu- 
tion and is usually very pure. It comes into the market precipitated 
in cakes £ inch thick, deposited on both sides of a thin plate of 
copper; or, after remelting, in ingots. Best selected copper is 
mainly used for the manufacture of alloys, as it is now prepared 
from pure materials. It is generally specified to contain not more 
than 0-05 per cent, arsenic, a trace of antimony, and no other dele- 
terious material. Tough copper is the name given in this country 
to refined copper cast into slabs or billets for rolling into sheets, rods, 
or tubes. It usually contains from 0-25 to 0-5 per cent, arsenic, 
from 99-5 to 99-2 per cent, of copper, and only small quantities 
of other impurities. 

The British standard specification for the testing of copper is as 
follows : 

Copper Plates for Locomotive Fire-Boxes. 

Tensile Mechanical Test. — A standard test-piece having a gauge 
length of 8 inches must show a tensile breaking strength of not less 
than 14 tons per square inch, with an elongation of not less than 
35 per cent. 

Bend Test. — Pieces of the plate shall be tested both cold and at a 
red heat by being doubled over themselves (that is, bent through 
an angle of 180°) without showing either crack or flaw on the 
outside of the bend. 

Stay-Bolts. 

The rods must be clean, smooth, uniform in diameter, and 
free from surface defects. The tensile test must not be less than 
41 tons, and elongation not less than 40 per cent. In the hammering 
or crushing down test, a piece of rod 1 inch long shall be placed on 
end, and hammered and crushed down to a thickness of -| inch 
without showing either crack or flaw on the circumference of the 
resulting disc. 



COPPER 179 

Copper Locomotive Tubes. 

Tubes must contain not less than 99 per cent, of copper and 
0-35 to 0-55 per cent, must consist of arsenic. Tubes must stand 
bulging or drifting without showing either crack or flaw, until the 
diameter of the bulged end measures not less than 25 per cent, 
greater than the original diameter of the original tube. 

Flanging Test. — The tubes must stand flanging without showing 
either cracks or flaws until the diameter of the flange is not less than 
40 per cent, greater than the original diameter of the tube. 

Flattening and Doubling-Over Test. — The tubes must be caj^able 
of standing both cold and a red heat, without showing either crack 
or flaw. A piece of tube is flattened down until the interior of the 
two surfaces of the tube meet. It is then bent so as to be doubled 




Fig. 89. — Photograph or Section Across a Weld Performed without a 
Special Phosphor-Copper Welding-Rod. 

Notice the numerous blowholes. 

over itself, bent through an angle of 180°, the bend being at 
right angles to the direction of the length of the tube. 

Hydraulic Test. — All boiler tubes shall be tested by an internal 
hydraulic pressure of at least 750 pounds per square inch. 

The oxy-acetylene welding of copper is not a stupendous job, 
but is as easy as with any ordinary mild steel stocks, provided that 
the necessary instructions are carried out in the operation of welding. 
It is not possible to weld copper with an ordinary copper rod. The 
copper when melted fuses, oxidation takes place, and the metal is 
burnt through overheating, its temperature reaching boiling-point 
in the attempt to make it weld. This leaves the copper weld full of 
blowholes and badly oxidised, as the above illustration proves. 

No matter what efforts are made to get good welds of copper, 
with only copper rods they would not be a success. It is necessary 
to have some flux to break down the oxide. The best method is to 



180 MODERN METHODS OF WELDING 

incorporate the flux in the welding-rod, which will afterwards be 
diffused in the molten mass as the melting takes place. If the 
welding is done with a proper anti-oxidising rod, it will be quite 
up to the other part of the article. 

The welding-rod of copper should contain a very small per- 
centage of phosphorus, with a trace of aluminium. The phosphorus 
is mixed with the copper when the rods are manufactured, in small 
quantities, evenly distributed throughout the rods, thereby securing 
equal mixture in the line of welding. It is very important that the 
proportion of phosphorus shall not be excessive, as this causes the 
metal to lack fluidity, and also leads to loss of elongation. The 
phosphuretted welding-rod is made in all sizes, from ^ to J inch 
diameter (the latter is used for welding repairs in locomotive fire- 
boxes). It is usually made in large, short, round bars, and drawn 
to the various sizes, which are then cut off to a length of 24 inches 
and bundled. 

In the welding of copper articles it is usual to employ, in combina- 
tion with the welding, a flux, or cleaning agent. There are several 
compositions of these fluxes. One very good one, which is largely 
used, consists of chloride of sodium 20 per cent., boracic acid 45 per 
cent., sodium borate 35 per cent. Another for copper alloy is: iron 
peroxide 35 parts, manganese peroxide 1 part, magnesium carbonate 
\ part, alum 18 parts, silica 3 J parts, borax 4 parts. Mix and stir 
well. Another consists of zinc oxide and charcoal in equal parts 
mixed with molasses water to a stiff paste, formed into balls and 
then dried. 

Copper welds should be prepared just in the same manner as for 
iron and steel; much more care and attention must be taken in 
cleaning the edges to be welded. If they are not well cleaned, the 
oxide or scale makes welding more difficult, sometimes causes adhe- 
sion, or gets internally into the weld and causes blowholes. 

With thin copper sheet it is imperative to have it supported 
underneath. If this is not done, the metal soon runs through 
owing to its fluidity, and it is very difficult to stop up the hole 
that has been made. It is the custom in some workshops to use 
a thick copper plate, which, on repetition work, assists the heating 
of the article welded. Sometimes asbestos board is used, but the 
author's experience is that asbestos wants renewing too often, as 
the workmen seem to pull it to pieces quickly. 

Further, there is a good smooth joint underneath, and welding- 
may go right through. But in the case of asbestos, if it goes 
through, the blowpipe usually burns or fires the asbestos, causing 



COPPER 181 

a dazzling light, and often leaves rough holes or surface on the 
underside. 

The power of the blowpipe for copper welding should be one 
size higher than that used for iron and steel, but the pressure of 
the oxygen should be reduced to its minimum. The larger pipe 
is needed because copper is a very high conductor. To counteract, 
to some degree, this conductivity, it is very necessary, too, to heat 
up the copper article before welding. 

The diameter of the welding-rod should be according to the thick- 
ness of the article to be welded, but slightly thicker than the same 
thickness for iron and steel. The minimum diameter is 16-gauge, 
but for general welding a stock of each size should be kept. A very 
good flux for copper is 2 parts cryolite, 1 part phosphoric acid. 
One has to be more careful in the welding of copper articles than 
with iron and steel, although the same procedure has to be followed 
out. An important point is the rapidity with which it must be 
welded. 

Also the weld must not be gone over twice, otherwise it will be 
burnt, oxidised, and full of blowholes. Another point, which must 
be watched, is that the melting-point of copper is 1,083° C, and the 
boiling-point 2,310° C. This difference in temperature is vital. 
When the melting-point is reached, welding must be proceeded with 
quickly, and the blowpipe must be passed smartly over the line of 
welding, so as to just melt and no more. The molten copper will be 
in the form of a viscous, thick liquid. The addition of phosphuretted 
rod will make a good clean weld, with a finish as smooth as the copper 
article itself. There will be no oxide, no blowholes, and the weld 
should stand any ordinary tests. 

On the other hand, if the welding is done slowly, and the blowpipe 
is held on the metal too long, the weld becomes too liquid by the 
extra heating of the metal. When the temperature is raised to a 
point near 2,310° 0., at which the copper boils, the metal is burnt. 
Oxides form, which are absorbed in the metal as it cools, and cause 
blowholes to form throughout the weld, making it defective and 
useless. 

Copper is the greatest conductor of heat of all metals. In 
welding, preheat it in a preheating furnace, if the facilities are 
at hand. Otherwise welding cannot proceed immediately owing to 
the necessity of preheating with the blowpipe to make up for the 
heat dispersing through the mass. 

Procedurs in Copper Welding. — When the article has been pre- 
pared, the blowpipe applied, and the welding-rod heldin the left hand, 



182 MODERN METHODS OF. WELDING 

melting starts at one end (at the same time the welding-rod being 
near the flame) ; the blowpipe is raised slightly to impinge the flame 
on the rod, which melts into the molten weld and unites therein. 
The blowpipe still continues melting in a progressive and continuous 
manner. Never let the white cone of the flame touch the metal, 
and take care to melt, not burn, the two edges of the weld. See 
that the metal remains a viscous liquid, and does not become 
" skilly," or thin liquid. Go through to the end of the weld 
without increasing the melting-point. A good weld may be 
hammered, bent, and annealed, and will stand the tests appearing 
in the first part of this chapter. 

The tip of the white jet of the flame should be kept y\ inch 
from the metal. The treatment after welding is important, for 





Fig. 90. — Microphotographs from the Region op a Weld Executed without 
Special Welding-Rod. 

Notice the separation of the crystals of oxide (deep black). The grey streaks in 
the section on the right are the eutectic alloy of copper, containing 4 per cent, 
of the oxide. 

without it the copper is inclined to be brittle. The whole article 
should be heated, and the weld vigorously hammered. After 
hammering, heat the article again to a dull red heat and plunge 
suddenly in cold water. 

Heated copper combines with oxygen, forming what is known 
as cuprous oxide. This oxide is absorbed in the molten copper, 
under the normal action of the blowpipe, and it crystallises on cooling. 
When oxidised to this extent, the weld is extremely fragile. The 
only means of overcoming this is, as before described, the use of 
a proper, skilfully prepared alloy welding-rod containing a very 
small percentage of phosphorus. 

The above illustration shows the oxide. 

The phosphorus welding-rod seems to have the property of pre- 



COPPER 1S3 

venting the formation of blowholes, either by suppressing the solu- 
tion of the gases, or by aiding their evolution before the tempera- 
ture of solidification. The phosphorus has the additional advantage 
of giving rise to a protective varnish on the surface of the molten 
copper. This is due to the formation of the oxide of phosphorus, 
which combines with the oxide of copper, forming a fusible green 
copper phosphate. This substance rises to the surface and protects 
the copper from further action of the gases of the blowpipe flame. 
Copper welds, when properly done, should be hammered where 
possible at a red heat, and then reheated and plunged in cold water. 
The sizes of copper phosphuretted welding-rods should be thicker 
than for mild steel ; for instance, I inch copper should have a -f\ inch 
diameter rod. As regards expansion, copper must be treated the 
same as cast iron — that is, all articles must be preheated, and 
annealed afterwards. 

Failures in welding copper can only be caused by : 

(1) Using a welding-rod of bad quality. 

(2) The absence of flux when the welds are not absolutely clean 

(3) Execution of the weld before the copper article is raised to 
a high tenrperature. 

(4) Bad joining of the metal and irregular feeding of the 
welding-rod. 

(5) The effects of expansion being badly opposed both during and 
after welding. 

(6) Getting the copper to too high a temperature, greatly 
exceeding the melting-point. 

(7) Going over the weld twice, not adding further welding-rod, 
thereby causing oxidation and blowholes. 

There are numerous applications in which the welding process 
may be adopted. As regards loco fire-boxes, it has been successful 
in some cases but not in others. Eor copper tanks, bends, rods in 
electrical work, copper bars and rings on armatures it is being found 
useful. Household copper boilers are being extensively welded; 
and there are many other directions in which welding could now 
take the place of brazing. 



CHAPTER XXIX 
BRONZE 

Bronze may be considered as an alloy of copper and tin, the former 
element predominating. Alloys with 1 to 2 per cent, of tin show 
nearly the ductility of pure copper. They can be worked in the 
cold state under the hammer more readily than pure copper. The 
ductility decreases rapidly with an increase in the content of tin. 
An alloy containing 4 per cent, can only be worked with the hammer 
at a red heat, and soon cracks when one attempts to hammer it 
cold. Alloys containing up to about 15 per cent, of tin can no longer 
be hammered, even in a warm state. Alloys with about 9 per cent, 
of tin show the greatest strength of all bronzes, and those with 
about 15 per cent, possess the greatest hardness and strength. The 
maximum of hardness and brittleness lies between 28 and 35 per 
cent, of tin. There are various bronzes on the market, those having 
a percentage of aluminium, manganese, phosphor, etc., being known 
by a double name — aluminium bronze, manganese bronze, etc., 
respectively. Some of these alloys are true bronzes, as they often 
contain no tin. 

Aluminium Bronzes. 

The proportion of aluminium alloyed with copper varies from 
1 to 10 per cent. The alloys are as strong as mild steel, highly 
malleable, elastic, and ductile. The presence of other metals 
impairs the quality. An alloy containing 10 per cent, has a tensile 
strength of 40 to 45 tons per square inch. 

Manganese Bronzes. 

These contain copper, manganese, zinc, and tin, and sometimes 
they are characterised by hardness, elasticity, and strength, com- 
bined with toughness and resistance to corrosion. They can be 
rolled and forged hot. An important application is for the propellers 
of steamships. They are also used in general engineering brass- 
work. The manganese is generally introduced in the form of ferro- 
manganese or as manganese copper. 



BBONZE 185 

Phosphor-Bronze . 

Phosphor-bronze contains a small proportion of phosphorus, 
introduced either as a phosphor-tin (obtained by dissolving 
phosphorus in molten tin up to 20 per cent, of phosphorus) 
or as phosphor-copper, after fusion, or the ordinary ingredients. 
The tin varies from 4 to 10 per cent, and the phosphorus from -1 to 1 . 
Where toughness and ductility are required the phosphorus should 
not exceed 0-1. Metals containing more, increase in hardness and 
are used for valves, bushes, cogwheels, etc. Phosphorus should 
be cast at as low a temperature as possible. 

Silicon Bronze. 

Silicon bronze contains silicon and is harder and stronger than 
ordinary bronze. The beneficial effects of phosphorus and silicon 
are generally attributed to the powerful deoxidising influence they 
exert on account of their affinity for oxygen. Bronzes do not absorb 
the heat like copper, although they absorb it more than iron and 
steel. There are several mixtures of bronzes, and one must be care- 
ful to use a welding-rod which is nearly the same mixture as the 
bronze article being welded. The table on p. 162 shows several 
varieties. 

Welding- Rods. — Welding -rods destined for the efficient welding 
of bronzes must be carefully manufactured from very pure metal, 
and their constituents must be the same as the article to be welded, 
with a small addition of phosphorus and a trace of aluminium. 
These rods should be carefully mixed when they are made, must not 
contain any impurities whatever, and should be made from new 
materials. They are made in sizes from jr to \ inch diameter and 
24 inches long. They should be sand-blasted if cast, so as to free 
the rods from the gritty sand. 

In the welding of bronzes it is necessary to have a cleaning flux 
to scour the metal as it becomes molten. The flux can be obtained 
from chemists who are skilled in the compounding of these mixtures. 
A good flux for bronze is equal parts of phosphoric acid and 80 per 
cent, alcohol. Others are equal parts of crude tartar and nitre 
burned together; and 3 parts nitre, 2 parts argol. 

Bronze Welding. — The first operation when one has a bronze 
article is to see if it is bevelled. If not, this must be done, and the 
weld properly cleaned and freed from all grease. It is usual to 
place the articles in the preheating furnace to get them hot to 
assist welding, and to prevent fracture from uneven heating. It is 



180 MODERN METHODS OF WELDING 

important if the article is unsupported on the inside to support it, 
as unless this is done the weld cannot be penetrated right through. 
The power of the blowpipe must be one size higher than that for iron 
and steel of the same thickness. The blowpipe must be properly 
regulated, and the oxygen must not be in excess, otherwise the weld 
would be oxidised and burnt. Likewise, if the acetylene is in excess, 
carbonisation will occur. The blowpipe must be well regulated until 
a clear white cone is reached, neither oxidising nor carbonising. 
Attention must also be paid to the pressure of the oxygen, which 
must not be more than that stated by the makers of the blowpipe. 
This is very important. 

Method of Welding. — The article should be fixed up usually in a 
horizontal position. If broken, the parts must be secured to pre- 
vent them from being out of line when welded. Proceed with the 
blowpipe (already properly regulated) to heat the edge of the line 
of welding, about \ inch from the actual edge, and start melting 
the two bevelled edges at this point. As soon as they become 
molten, add a little welding-rod, to which is annexed the flux, and 
then bring the blowpipe to the edge of the weld. Bring this to a 
molten state, add welding-rod, fill up bevel, and proceed forward 
with the welding, at the same time giving a regular gyratory move- 
ment. Both edges of the weld must be melted together simul- 
taneously with the welding-rod with an occasional dip in the flux. 
See that the rod is kept sufficiently in the molten metal to fill up 
the bevelled edges to the same thickness as the article being welded. 
One must not go over the weld twice without adding fresh metal. 
If this is done oxidation takes place and the weld is full of blow- 
holes and spoilt. 

As soon as the weld is done, the article must be put into the 
annealing furnace and heated up to about 600° C. and then allowed 
to cool down slowly. 

Failures in welding bronzes are due to : 

(1) The use of an impure welding-rod. 

(2) The overheating of the metal, making it too fluid and caus- 
ing oxidation and blowholes. 

(3) The weld being gone over twice, leading to oxidation. 

(4) Insufficient penetration, causing adhesion. 

These failures can easily be overcome if operators practise regu- 
larly, and test their pieces until they find out that they have become 
proficient. 



CHAPTER XXX 

BRASS 

Brass is an alloy of copper and zinc, and is in most general 
use. It should only contain copper and zinc, but most varieties 
contain small quantities of impurities. Copper and zinc can be 
mixed together -within very wide limits, the resulting alloys being 
always serviceable. 

Generally speaking, it may be said that with an increase in the 
content of copper the colour inclines more to golden, the malle- 
ability and softness of the alloy being increased at the same time. 
With an increase in the content of the zinc the colour becomes lighter 
and finally shades into a greyish-white, while the alloy becomes 
more fusible, more brittle, and at the same time harder. The physi- 
cal properties of brass varj^ according to the relative quantities of 
copper and zinc. Alloys containing up to 35 per cent, of zinc can be 
converted into wire and sheet in the cold state only, those with from 
15 to 20 per cent, being most ductile. Alloys with from 36 to 40 
per cent, of zinc can be worked in the cold state as well as the hot. 
With a still higher content the ductility increases rapidly; and an 
alloy, for instance, from 60 to 70 per cent, of zinc is so brittle that 
it cannot be worked. If, how r ever, the zinc is increased up to a 
maximum (70 to 80 per cent.), the ductility increases again, 
and the alloy can be worked quite well in the hot state, but 
not at red heat. The strength of brass is intimately connected 
with its composition, that containing about 28-5 per cent, of 
zinc showing the greatest absolute strength. The strength depends 
to a great extent upon the mechanical treatment the metal has 
received. 

An important factor in brass is its melting-point, there being 
wide deviations in this respect, which are readily explained by the 
great difference in the melting-points of the two constituent metals. 
Generally speaking, the fusing-point of brass lies at about 1,832° F. 
The mixtures for certain purposes are legion. 

Hot-rolling 70/30 Brass.— It is quite possible to roll this metal 

187 



188 



MODERN METHODS OF WELDING 



hot by using electrolytic copper and an electrolytic spelter. 

The following is the mixture : 

Pounds. 

.. 68 

2 

. . 30 



Electrolytic copper 
Cupro-manganese (25 per cent.) 
Brunner-Mond electrolytic spelter 



The metal rolls well at a bright red heat, but is more expensive 
than ordinary brass. 

Admiralty Specification for Brass. 

The composition of the mixtures used throughout the whole of 
the work supplied is to be as follows. New metal only is to be used 
for castings subject to steam pressure. 



Tin. 



Zinc. 



Copper. 



Naval brass 

Brass for condenser tubes 



37 
29 



62 
70 



All brass subject to the action of sea water must not in any case 
contain less than 1 per cent, of tin. 

Tensile test-pieces taken from castings must stand the following 

tests : 



Ultimate Tensile 

Strength Not Less 

Than 



Naval brass round bars, £ 
Naval brass round bars, above f 
High-tension brass, forged 
High-tension brass, cast 



14 tons 
26 ,, 
22 ,, 

28 ,, 



Elongation in 
Length of 2 Inches. 



1\ P er cent. 
30 
30 
25 



Naval bars must be capable of : 

(a) Being hammered hot to a fine point. 

(b) Being bent cold through an angle of 75° over a radius equal 
to the diameter of the bars. Breaks within less than | inch of the 
grip are not accepted. 

General. — The metal castings are to be sound, clean, and free 
from blowholes, and no piecing, parching, or stopping will be per- 
mitted. 

The above articles are often welded, and one must study their 
elements in order to be able to execute satisfactory welds on them. 



BRASS 



189 



Brasses are bad conductors, but quite as fluid as copper. There are 
two classes of brass — first and second qualities. The first melts at 
930° C.j the second at 880° C. This is important, as if they are got 
to high temperature they burn, the zinc volatilises, and the metal 
is oxidised. The melting of brass under the action of the blowpipe 
is accompanied by the phenomena of the absorj)tion of gases, 
volatilisation of zinc, and oxidation. 

Operators must not attempt to weld brass autogenously with- 
out understanding the metallurgical idiosyncrasy, otherwise success 
will not be obtained. Much trouble springs from the volatilisation 
of part of the zinc, which rises in dense white fumes. Blowholes 
then abound, part of the zinc is lost, and the weld has no strength. 

Welding-rods for the welding of brasses are manufactured in the 
same way as copper rods, and should be as near as possible in com- 
position to the metal being welded, so as to keep the same mixture 
of alloy as in the article itself. It is usual in shops where a variety 
of brass castings are welded to keep sets of welding-rods made up 
to the different analyses to suit the castings. These rods can be 
obtained from the various manufacturers who make and stock them. 

Rods for brasses are made from the purest new metal, in which 
a minute quantity of aluminium should be evenly incorporated 
throughout the length of the rod. They are made in various sizes, 
from ^ to | inch thick. In conjunction with the rod a cleaning flux 
must be provided, which dissolves the alumina, prevents the vola- 
tilisation of the zinc, and protects the metal from oxidation. There 
are many fluxes in use, but for general purposes the following give 
good service: 

[ Chloride of sodium .. .. 30 per cent. 

(1) -Boric acid 
(Borax 

ii\\ | Selenium 
(wj \Charcoal 

[Sodium carbonate 
/q\ | Silica (white sand) 
^ ' 1 Coal dust (anthracite) 

[Bone ash 



40 


55 


30 


55 


2 


parts 


1 


part. 


5 


parts 


15 


55 


5 


55 


20 


55 



Execution of Brass Welds. 

The edges are prepared as for iron and steel, according to the 
thickness, on one side or both. If it is a case of castings, these two 
must be bevelled wherever the crack or break occurs, otherwise one 
is sure to get adhesion or lack of penetration, excessive consumption 



190 MODERN METHODS OP WELDING 

of gases, burnt metal, and a defective weld. This bevelling cannot 
be insisted on too much. The bevel must be 90° to the thickness 
of the metal — that is, 45° each side. Brass, more than metal 
(aluminium excepted), must be thoroughly cleaned, otherwise 
adhesion takes place. Brass welds are easy to do and give good 
all-round results, but only when the weld line is properly bevelled 
and clean. Also it is advisable to preheat the article to just under 
500° C. 

The blowpipe used is the same as in the case of copper: one 
size larger than for iron and steel. The size has been selected to 
suit the thickness of the articles being welded. For instance, 
75- inch thick requires a blowpipe consuming IT cubic feet of acety- 
lene per hour — that is, size 2 blowpipe. The welding-rod for ^-inch 
thick metal should be ^ inch diameter. 

It is essential to have a rod a little thicker than the metal to be 
welded in the case of brass. Many brass articles require to be 
supported underneath the welding line, to allow good penetration of 
the weld. In welding, the blowpipe should be started a little from 
the end (about | inch), so as to preheat this part prior to doing 
the starting edge. When this part is beginning to become molten, 
just put your blowpipe on to the edge. At the same time add the 
welding-rod to fill and cover up the bevel, and then proceed along 
the line of welding, melting both edges of the article and the feeding- 
rod at the same time. Continue advancing with a gyratory move- 
ment and adding with regularity the welding-rod, which must be 
dipped in the flux from time to time, according to progress made. 
Welding must be continuous until the whole line of welding is com- 
plete. The welding must be rapid, far faster than with iron or 
steel. Care must be taken not to let the blowpipe stay too long- 
on the weld, or it will burn, and will increase the temperature, and 
cause the metal to boil and bubble, which no flux or rod will check. 
Consequently the weld will be full of blowholes, the zinc will be 
reduced, and the weld will be oxidised, and therefore useless. 

To avoid these failures one must not use a rod of bad mixture, 
nor let the blowpipe remain too long on the weld, otherwise the metal 
" boils." The white jet must not touch the metal within ^ inch. 
Brass of the first quality can be hammered and annealed, and can 
stand energetic forging or stamping without showing fracture. 
This hammering improves considerably its mechanical properties. 
Brasses containing 55 to 65 per cent, of copper should be forged hot, 
those containing 65 to 70 per cent, of copper hammered cold. After 
hammering, brass should be annealed to just under 500° C. 



CHAPTER XXXI 
AMERICAN METHODS 

Operators will benefit by an insight into what the Americans are 
doing in the way of welding processes. Shortly after the United 
States entered the war, the Council of National Defence appointed 
an Engineering Committee, which undertook as one of its chief 
tasks a study of the possibilities of electric welding in shipbuilding. 
This Committee was taken over by the Emergency Fleet Corpora- 
tion. It later broadened its scope so as to include gas and thermit 
welding. By its discussions, researches, lectures, and conferences, 
its interchange with foreign countries and its dissemination of in- 
formation, the Committee gave a great impetus to the use of welding 
in America. 

Concurrently with this work, another advance in welding, with 
an emphasis on gas welding, was started by the formation of the 
National Welding Council. With industry becoming normal, after 
the Armistice, it was considered desirable to extend into the entire 
field of joining metals, and an effective way of accomplishing this 
was the foundation of the American Association for the Welding 
Industry. 

The Society was brought together in the manner usual with 
scientific societies : persons from all branches of the industry interested 
in any of the welding processes — forge welding, electric resistance 
welding, thermit welding, gas welding, electric spot, butt, seam, and 
arc welding. It will create and assist in maintaining the Bureau 
of Welding, which will be a separate organisation, designed to take 
full advantage of the principle of co-operation in research and 
standardisation. Some of the Society's investigations may be cited. 

(1) In arc welding a determination of the best current with 
various sizes of electrodes. 

■ (2) A determination of proper methods of procedure in making 
arc and gas welds, with a system of inspection as the work pro- 
gresses. 

(3) The acquirement of further knowledge of the characteristics 

of metal as affected by welding, particularly its ductility and its 

action under repeated tests. 

191 



192 MODERN METHODS OF' WELDING 

(4) In gas, spot, or arc welding methods of assembling large 
structures to eliminate initial or locked-up stresses, due to contraction 
on cooling. 

(5) The ascertainment of a proper standard for both producer 
and consumer. For some years numerous overlapping and con- 
flicting efforts in the field of industrial standardisation have been 
carried out by more or less independent organisations, each according 
to its own methods of procedure. There was need, therefore, of 
reducing unnecessary effort, and providing uniform methods that 
will secure in each case the co-operation and support of all the 
organisations whose interests may be affected. 




Fig. 91. — Duograph Welding Machine. 

Training of Operators. — The investigations of the Welding Com- 
mittee have thus far shown that one of the most important elements 
in the success of an autogenous welding operation is the skill of the 
operator. To secure this, uniform methods of training are essential. 
The Society is taking an active part in planning how operators should 
be trained and how their proficiency may be determined. Some 
of the objects of the American Society are as follows: 

(1) To advance the art and science of welding. 

(2) To afford its members opportunities for the interchange of 
ideas with respect to the sciences and art of welding, and for the 
publication thereof. 

(3) To conduct researches into welding, co-operating with other 



AMERICAN METHODS 



193 



societies and associations, and with the Governmental departments, 
for the benefit of the industry generally. 

The illustration on previous page is of an automatic seam-weld- 
ing machine, which is known as the "duograph." This machine, 
specially designed for welding the seams of drums or containers, 
ensuring a mechanical weld uniform in appearance and efficiency, 
comprises a turret-top holding device, with water-cooled arms and 
clamps for holding the steel drum in position, permitting of the 
form being placed in position for welding on the one set of arms, while 




Fig. 92. — Showing Different Operations of the Duograph. 



the form on the opposite set is being welded. The turret top is 
then swung half-round, the welded form removed, and another set 
up ; this preparation requires less time than the actual welding of the 
form in position. The blowpipe carriage is moved forward at a fixed 
speed of welding, by a power-belt motor driven, and is reversed by a 
hand wheel when the weld is finished. 

Variable speed for different thicknesses of welding is obtained 
by the use of cone pulleys. The blowpipe carriage is fitted with two 
blowpipes, one above and the other below, for welding both sides 
of the seam simultaneously. For very light welding, one blowpipe 

13 



194 MODERN METHODS OF WELDING 

only is required, welding from one side. Water-cooled blowpipes 
are used, connected with rubber tubing to the water-supply. 

This machine will weld a seam 36 inches long. An average speed 
of welding is 18 inches per minute, or 90 feet per hour may be obtained 
on 16-gauge sheets. 

The photograph on p. 193 shows different operations of the duo- 
graph. 

Fig. 93 is of a medium-pressure acetylene generator, 15 pounds 
pressure as a maximum. This is designed to provide acetylene 
under suitable conditions and with proper control, to meet the 
requirements of the oxy-acetylene welding and cutting, and to 
make possible the employment of the positive-pressure principle, 
utilising acetylene under direct and appreciable pressure, employ- 
ing lump carbide for the generation of the gas, with indepen- 
dent power for feeding the carbide, the feeding mechanism being 
controlled by the gas pressure as generated : the carbide drops into 
large voHmes of water, cools the gas, and generates slowly. 

Safety has been given even greater consideration in the con- 
struction of these plants than efficiency. They have automatic 
feed, carbide to water, with independent power, and the quan- 
tity of carbide remaining in the hopper is constantly indicated. 
The acetylene gas is piped directly from the generator under 
requisite pressure through a service pipe-line to the welding 
stations, and regulated by reducing valves, fitted with pressure 
gauges to govern the proper working pressure. 

These are made in many sizes to most economically meet the 
requirements of the purchaser, and may be had with capacity of 
25, 50, 100, 200, and 300 pounds of carbide constituting a full charge. 
These generators are exceptionally economical compared with the 
low-pressure system. The latter are used almost exclusively in 
England. The blowpipes used in low-pressure consume from 1-5 
to 1'3 parts of oxygen to 1 part of acetylene. The medium-pressure 
generators consume 1 part of oxygen to 1 part of acetylene. 
Hence, therefore, medium -pressure generators save 40 to 50 per cent, 
of oxygen over the low-pressure, also the medium-pressure gives 
40 per cent, more welding. Their blowpipes never back-fire; they 
keep in all day. Perfect welds are obtained ; no adhesion, no oxida- 
tion, fully penetrated welds with 98 per cent, tensional stresses. 
These advantages are attainable from the generators referred to, 
which are known as the Davis-Bournonville. They are built from 
heavy steel plates, and galvanised after manufacture. They are used 
in very many workshops in the U.S.A., and give every satisfaction. 



AMERICAN METHODS 



195 



This medium-pressure avoids the defects of the low-pressure 
types, which depend solely on the injector principle for the proper 
mixture of the gases imperative to securing the best results. It will 
be readily understood that in successful welding a neutral flame 
must be employed, because if there is any excess of oxygen the metal 




Fig. 93. — 200 Pounds Carbide Capacity, using If Pounds Carbide. 
Height, 104 inches; diameter, 37 inches; weight, 850 pounds. 

will be burnt and oxidised. By putting the gases under pressure 
instead of depending largely on the injector principle, a positive 
control of the gas is obtained. 

Some of the most extensive work carried out in America was a 
twelve months' job for eleven welders, welding a metal-roofed flue, 



196 MODERN METHODS OF WELDING 

850 feet long and 120 feet wide, constructed with 690,000 No. 9 
gauge plates. This job employed 200 tons of carbide in two 200- 
pounds capacity generators by Davis-Bournonville Company, with 
330,000 feet of oxygen and 9,200 pounds of y\-inch thick welding- 
rods, for 53,365 lineal feet — or over ten miles of welding. 

A notable welding job was the saving of 9,000 feet of 4 to 6 feet 
diameter power pipeline, averting a loss of several hundred thousand 
dollars, in the Colorado Mountains. The joints were leaking, and 
over 4,000 feet of the heaviest portion of the pipe had been discarded 
as impracticable; but the workmen carried on for several months 
during the winter. 

Nearly a mile of cutting was recently done by a single Davis- 
Bournonville operator in Northern Canada. About two weeks' 
intermittent operation was required, averaging about 350 lineal 




Fig. 94. — Part Section, Non-Flash Blowpipe. 

feet per day, making 5,097 lineal feet of cutting of a steel pipeline, 
12 feet in diameter, 1,480 feet long. This was cut into two half- 
sections, and the upper half into sections for removal. The last 
85 feet was done in sixty-five minutes. 

Range boilers are welded at 30 feet per hour. 

Barrel seams (30 inches long, by 20-gauge thick) are welded at 
the rate of 75 to 85 seams per day. 

An immense hydraulic press was repaired at a cost of about 
$350, saving the owners about $1,000 per day for sixteen 
days. 

A Corliss compound engine, 2,500 h.p., was repaired in four days. 
There was one crack 14 inches long, another 23 inches long, and still 
another 5 feet long. It was estimated that the cost of a new casting 
would have been $2,000, not including the cost of dismantling and 
reassembling; and the new casting could not have been procured in 
less than six weeks. 



AMERICAN METHODS 



197 



Others that would heretofore have been considered marvellous 
operations have been performed by the oxy-acetylene process, 
but sufficient has been said to convince the readers of its 
adaptability. 

Another novel but useful tool is a blowpipe just brought out in 
America which is known and sold as the " rego " bloAvpipe. It is 
claimed that these torches do not, and cannot, flash bach. This is 
owing to an arrangement in the blowpipe which is designed for 
special supply and mixing chambers. The acetylene must be higher 





Fig. 95. — Air-Gas Preheating Torch 
Flame Playing on Mixing Chamber 
oe Welding Torch until Tip and 
Nut are Red-Hot. No Flash. 



Fig. 96. — Welding Torch Tip Directly 
on Metal at White Heat, Held 
There till it Penetrates. No 
Flash. 



pressure than the oxygen, but not exceeding 15 pounds. The claim 
is made that this invention imparts to the acetylene a sufficient 
speed as it enters the mixing chamber and commingles with the 
oxygen to ensure that at this point, with a neutral flame burning at 
the tip, the speed of both gases shall be greater than that of the 
flame propagation of the mixtures at the point where the gases 
commingle. 

The acetylene must be under greater pressure than that of the 
oxygen to obtain this result. The heating of the chamber at this 
point to a sufficient degree to ignite the mixed gases will not cause 
a " flash back," since the speed of the mixture will carry the flame 



198 



MODERN METHODS OF WELDING 



to the tip. If obstructions, such as flying particles of molten metal, 
or the bringing of the blowpipe close, or up to, the metal, reduce 
the velocity of the mixtures at the tip and tend to drive the flame 
into the interior of the pipe, the acetylene, being under greater pres- 
sure, immediately seals the oxygen, causing a carbonising mixture 
to flow from the mixing chamber to the tip and ignite. As the car- 
bonising flame cannot flash back, the acetylene alone, or with some 
quantity of oxygen (depending upon the size of the obstruction), 
continues to burn at the tip until the obstruction is removed, when 
the oxygen again flows through in full volume, producing a natural 
flame. 

The American Welding Committee of the Emergency Fleet Cor- 
poration, under the chairmanship of Professor C. A. Adams, has been 




Fig. 97. 



-Welding Torch Tip Directly against Brick. No Escape for Heat 
Waves except against Tip. No Flash. 



of great assistance to the welding industry. At the second meeting 
held, a communication was received from the U.S.A. Shipping Board, 
requesting information and advice on the most economical method 
of producing anchor chains in large quantities. A meeting of repre- 
sentatives of chain manufacturers was arranged, and the work was 
put in hand. In six weeks a sample was submitted. Within six 
months production on an order of $1,000,000 for chains made by a 
new process saved the Government $£0,000 at the start. This new 
chain, made from cast steel, refined in an electric furnace, not only 
met the specifications of the carefully hand-forged chains of the past ; 
but in place of the average production by a gang of chain- welders of 
the highest skill of less than 1,000 pounds per day, a foundry unit 
with a 10-ton electric furnace produced 70 tons of 2-inch chain in 
twenty-four hours, with mostly unskilled labour. 



AMERICAN METHODS 



199 



At the same meeting plans for spot welders of the portable type, 
for from J up to 1 inch plates, were discussed. Under the leader 
ship of H. M. Hobart, the Research Committee investigated the 
current density suitable for various electrodes; non-destructible 
methods of testing welds; the effects of locked-up stresses in weld- 
ing long sections by rigid or non-rigid methods; the methods of 
holding plates during welding ; the effect of corrosion on welds and 
adjacent metal, conducting a series of tests on J-inch plates welded 
by employees of the manufacturers 
who supplied the apparatus — the 
choice of electrodes, current density, 
and method of control being left to 
the discretion of the welders. They 
finally submitted standard methods 
for testing electrodes for welds of all 
kinds, and revised specifications for 
electrode wire. These tests are known 
as the Wirt- Jones. As the result of 
this instruction propaganda, the Ship- 
yard Visiting Committee reported 
that at Hogg Island alone hundreds 
of thousands of parts were being 
welded instead of riveted, the saving 
being approximately 70 per cent. 

Electric welding is used very ex- 

tensively in America; the General ^^-^^t^Z^T^ 
. J ' 5-Inch Axle, Tip in Hole. JNo 

Electric Company are extending the Escape for Sparks or Heat 
production of equipment for electric except against Tip. No Flash 
welding for all classes of work. I 
propose to show some of the equipment in general use later. 

During the past few years the extension of welding of all kinds 
to the building and repair of ships has been phenomenal, especially 
as regards electric welding. While electric welding has been used 
chiefly for iron and steel, the technique of the art for cast iron and 
the various non-ferrous alloys employed in shipbuilding is being 
rapidly developed. The welding of copper can be done with the 
carbon electrode. Brass and bronze castings and flanges welded to 
the pipes are very common. 




CHAPTER XXXII 
THE METALLURGY OF ARC WELDING 

We have learned to know, with a fair degree of certainty, what a 
steel casting should be to be acceptable for any given engineering 
purpose. We are apt to be very particular about casting when human 
life would be in danger by its failure in service. This is true of all 
iron and steel parts, which go largely to the make-up of our present- 
day necessities. 

In building up and bringing together many scattered facts about 
the behaviour of iron and its alloys, under varying conditions, the 
microscope has played a very important role. It satisfies the natural 
curiosity to " see what's going on." Merely to see a line of signal 
flags on a destroyer, however, does not help us much unless we know 
what the signals mean. Just so an intelligent investigation of a 
metallurgical product, like a weld made by an electric arc, involves 
considerably more than a mere examination of the metal or its frac- 
ture under the microscope, much as this may reveal. 

The making of a good weld is essentially a metallurgical problem. 
More specifically an arc weld is a steel casting made by a continuous 
process both as regards melting and casting, i What we require is a 
sound, fine-grained casting, free from blowholes and slag inclusions 
and low in impurities. The casting must also make a continuous 
and perfect union with the plate or material to be welded. The 
physical properties of the weld will depend upon five distinct factors, 
namely: (1) Crystal structure; (2) gas-holes; (3) slag inclusion; 
(4) impurities ; and (5) composition. These factors are identical with 
those determining the properties of any steel product, with the ex- 
ception that most of the latter may be improved by heat treatment 
or working, while in a large majority of cases the weld must be used 
as made. The order in which these factors are given is not to be 
taken as the order of their importance; the time has not arrived 
when such an order can be set down. 

Crystal Structure. — In studying the crystal structure of a large 
number of welds, as revealed by fracture, it appears that a very 
fine grain is produced by depositing the metal rapidly in compara- 

200 



THE METALLURGY OF ARC WELDING 



201 



tively thin layers, thus preventing the plate from heating up suffi- 
ciently to slow down the cooling. As soon as this occurs, columnar 
crystals begin to form, with a resulting brittleness. 




Fig. 99. — Showing Areas at High Magnification. 

It is often desirable for other reasons, however, to maintain 
as large a molten pool as possible. In such a case, the only way 
to maintain a fine structure is to hammer the weld while hot, to 
prevent the formation of too coarse a structure. The cooling effect 




Fig. 100. — Nitride Areas in Electrolytic Iron treated as Fig. 102. 



of the plate upon the weld structure may be readily observed in 
running a short length of weld across a plate. The first part of the 
weld will show a fine-grained fracture, while a little farther along 



202 



MODERN METHODS OF WELDING 



a decided growth begins, gradually changing to an entirely coarse 
structure as the plate heats up. Methods of keeping the plates 
cool with a stream of water have been tried with considerable success 




Fig. 101. — Electrolytic Iron, Nitrogenised by Annealing in NH 2 Twelve 

Hours, 750° C. 

as far as the grain-size is concerned, but difficulties of manipulation 
have prevented its adoj)tion in practice. 

Gas-holes are to be found in all electric welds, and are an inipor- 



a* 

p' 1 




•' * y 




tot/'' ' - 

& • ■ ■ 




-■ y.-^.t ... 


■ ■■'■"''. ,' k*i 






'V : vr^ . 


'• '-' ' - *'\ 






■ : '* >-". : ■ 


'... ^3 



Fig. 102. — Electrolytic Iron, Nitrogenised by Annealing in NH 2 Twelve 
Hours, 750° C, but subsequently Annealed in Vacuum for Two Hours 
at 1,000° C. Areas Smaller and Lines Diminished in Number. 

tant source of weakness. Their occurrence is frequently attributed 
to the presence of dissolved gases or gas-forming impurities in the 
electrode material. This is undoubtedly true, but only to a limited 



THE METALLURGY OP ARC WELDING 



203 



extent. Dissolved or occluded gases in electrodes are largely liber- 
ated as the metal passes through the arc stream, and cannot have 
any considerable effect upon the deposited metal. They do affect 




Fig. 103. — Edge of Weld made with Covered Electrode, showing Coarsen- 
ing op Grain in Plate Stock by Overheating. (Unannealed.) 

the working of the electrode, however, as they cause spluttering, 
frequently so bad as to make the electrode useless. Experiments 
have shown this to be particularly true of highly oxygenous 



Hit* I 



m 



j 



:r*>* 







H 



m mm 

mm? 



Eig. 104. — Unannealed Weld Section. Weld made with Standard Bare 

Wire Electrode. 

electrode steel. Carbon is one of the worst offenders in producing 
gas-holes. Always ready to combine with oxygen, it finds a rich 
supply in the metal deposited by the arc. Carbon monoxide is 



204 



MODERN METHODS OF WELDING 



formed and, owing to the rapid solidification of the metal, is trapped. 
The carbon in the plate also becomes an important factor in this 
connection. The carbon in that portion of the plate dissolved 













f, 












Fig. 105. — Lines in Weld Annealed. 

into the welding pool reacts with the large percentage of iron oxide 
contained therein and forms more carbon monoxide, which has no 
opportunity to escape. Welds made on carbon-free iron do 'not 




Fig. 106. — Slag Enclosed in Weld. 



always appear in this particular form, as may be seen where the 
most highly nitrogenised sections show up as dark patches not unlike 
pearlite. These are shown under higher magnification in Figs. 99 
and 100. 



THE METALLURGY OF ARC WELDING 205 

Nitrogen is one of the most effective elements for making steel 
brittle. As little as 0-06 per cent, will reduce the elongation on a 
0-2 per cent, carbon steel from 28 to 5 per cent. Nitrogen is con- 
tained in regular steel only in very small amounts, varying from 
0-02 per cent, in Bessemer steel to 0-005 per cent, in open-hearth. 
Under ordinary conditions of fusion, nitrogen has little effect on 
iron, but under the conditions of the electric arc it becomes much 
more active. The elimination of these nitrides and oxides must be 
accomplished before the weld can be made ductile. Many attempts 
have been made to do this by the alloying of various scavengers with 
the electrode material, or by painting them on or in some way 
attaching them to the electrode. Among other impurities that 
may occur in a weld, the sulphur may combine with the manganese 
present. 

It is doubtful if enough sulphur will remain in the weld section 
to do any great harm. Phosphorus forms a dangerous phosphide 
eutectic with iron, which tends to form a brittle envelope around the 
crystals. 

Composition. — -By composition, given as the fifth item influencing 
the quality of the weld, is meant the intentional addition of such 
elements as nickel, tungsten, or the like. These elements in varying 
proportions are added to steel to impart specific properties. One other 
item which must receive consideration is the effect of overheating 
the plate during welding. In all welds on fairly heavy sections, this 
effect is always present, and not infrequently so weakens the metal 
as to cause it to break just outside the weld, giving rise to mistaken 
ideas that the weld is better than the metal welded. This overheating 
causes a coarsening of the grain in the metal (see Fig. 103), and the 
segregation of the pearlite into large masses enclosed in ferrite enve- 
lopes. In general, it must be said that much depends on the opera- 
tor, and much difficulty is experienced on this account in comparing 
data from several sources. Great difference of opinion still exists 
on many of these points, but the co-operation of the welding interest 
is making rapid strides towards placing the whole art upon a more 
scientific basis. 



CHAPTER XXXIII 
BRIEF DESCRIPTION OF ELECTRIC WELDING 

Electric butt welding is a method of fastening together suitable 
pieces of metal by the creation of intense heat at a desired place 
through the proper application of electricity, jointly with pressure 
if butt, seam, or spot welding. The pressure must be applied — 
if the work is to be efficient — in increasing ratio, before and after 
the application of the electric current. The time taken to make a 
weld varies from one-fifth of a second to four or five minutes, 
according to the area welded. The current required is of high 
amperage {i.e., volume), but at low voltage (i.e., pressure). 

Volts x amperes = watts. 
1,000 watts = 1 kilowatt. 
746 watts = 1 horse-power. 

The pressure is applied by hand or foot, by spring, or by hydrau- 
lic means, according to the nature and size of the work to be welded. 
There is no danger. The voltage or pressure used in the electrodes 
and the exposed portion of these machines is so low — being from 
only 2 up to, possibly, 5 volts at the most — that no one would feel 
an embarrassing shock therefrom. It is about equivalent to the 
voltage or pressure of an ordinary push-bell. Subsequently, heat 
has no effect upon the weld, unless the heat is of such an intensity 
as to remelt or burn the metal; no less degree of heat will affect it. 

There are four main divisions of electric welding, namely : 

Spot Welding. — This, as its name implies, is a process which con- 
sists in welding articles together in spots instead of riveting them. 
The spots are usually T V to J inch in diameter, seldom larger. 

Seam Welding. — This is a process whereby the overlapping edges 
of metal are joined together by fusing. 

Butt Welding. --This process consists in bringing together, or 
butting, the two ends of the metal rod, bar, etc. (not overlapping), 
thereby causing them to fuse one into the other. 

Arc Welding. — This process is used for filling in new metal along 
the joints to be welded, the electric current melting both faces to 

206 



BRIEF DESCRIPTION OF ELECTRIC WELDING 207 

be welded at the same time as the electrodes, and filling up the joint 
to the level of the plate. 

In spot welding the electrodes on various machines may vary 
from § to | inch or more in diameter. They should be tapered 
similarly to a pencil, at an angle of about 45°, to a dull point. The 
point should be slightly less than the diameter of the weld. This 
may cause a marking or pitting of the metal where the weld takes 
place, which can be avoided on the mild steel about 20- to 28-gauge 
by using flat electrodes on one or both sides. On thicker materials 
one flat electrode can be used. 

Relative Cost of Riveting and Electric Spot Welding. — Riveting 
requires, in labour, the marking off, punching, and drilling of both 
the plates so that the holes match, and the actual operation of 
riveting. Then there is, of course, the purchase cost of the rivets. 
The result attained is two pieces of metal held together by a softer 
metal. As they are held chiefly by the pinch between the two rivet 
ends, working is likely to take place, for the rivets seldom fit the 
hole tightly. 

Spot welding saves the cost of rivets and most of the labour. 
There is no marking off, no holes to punch, no rivets to fit in the 
holes. The welds can be applied at a speed varying, in continuous 
succession, from a few to over 100 per minute. In fact, on certain 
kinds of work, 200 welds can be applied per minute. The welding 
machines on light work are capable of making a weld every fifth 
of a second, the speed depending upon the ability of the operator; 
and in all repetition work the spot welding costs are 75 per cent, 
less than riveting. 

Metals Suitable few Spot Welding. 



Platinum to steel or iron. 

Silver to brass, steel or iron. 

Aluminium. 

Phosphor - bronze to self and 

brass. 
Brass to self, steel, and iron. 



Copper to self, with a thin brass 

insertion. 
Steel to self, iron, and metals as 

above. 
Iron to self, steel, and metals as 

above. 



Cast iron is not weldable by this process. 

Butt welding is principally used for repetition work, joining 
together bar metal for crankshafts, drop forging, to stock bars, 
tyres for cars and waggons, bands for oil drums, rings, chains, mild 
steel to high-speed steel, etc. The scope is from wire the thickness 
of hair to 15 inches square. 

Seam welding is used for making watertight joints, where spot 



208 MODERN METHODS OF WELDING 

welding would not suffice. Seam welding consists of welding to- 
gether the overlapped edges of two sheets of metal by heating under 
pressure, with copper rollers or wheels. 

Usually the combined effect of the pressure and the heat causes 
the welded seam to be nearly the same thickness as the original 
stock. It is, however, limited in its application to thinner material, 
and aluminium cannot be welded. 

Early in 1902 there was a demonstration in Milwaukee of the use 
of the electric arc for the cutting of steel. An enormous boiler founda- 
tion had to be removed from the basement of a building, so heavy that 
local mechanics despaired of being able to cut it. The electric arc 
was requisitioned and soon cut (or, more correctly, burned) the steel 
plate at the rate of 1 foot in five minutes, so that in a short time the 
whole plate was divided in blocks and transported away. 

Electric track welding has become an important business. 
Rail joints are welded together just as they lie on the ties. The 
first operation is sand-blasting to free the rail ends from dust and 
dirt. An apparatus resembling a horseshoe is placed over the 
rails where they join; then, strips of steel having been placed on the 
sides of the joint, the current is turned on. The metal of the joint 
soon rises to a welding heat. The current is next shut off and the 
hydraulic jaws produce a great pressure which completes the weld 
quickly. The current used is from 25,000 to 30,000 amperes at 
7 volts. The supply at the welder is regulated at about 30 volts. 

Operators often ask, What is a volt ? This is a term used to 
represent the pressure of electrical energy. In steam we would say 
that a boiler maintains a pressure of 100 pounds. This term relates 
to pressure only, regardless of quantity, just as the steam pressure 
of a boiler has nothing to do with its capacity. 

An ampere is a term used to represent the current. In the case 
of steam or water we speak of the carrying capacity of a pipe in cubic 
feet, while in electricity the carrying capacity of wires is given in 
amperes. 

A watt is the electrical unit of power, and equals volts x amperes. 
One watt horse-power is equivalent to lj mechanical horse-power 
A kilowatt-hour, or k.w.h., is the electrical equivalent of mechani- 
cal work, which would be stated in the latter in the terms of horse- 
power. It means the consumption of 1,000 watts of electrical 
energy steadily for one hour or any variation thereof (such as 5,000 
watts for twelve minutes), and it is the unit employed by all power 
companies in selling electrical power, their charges being based on a 
certain rate per k.w.h. consumed. 



BRIEF DESCRIPTION OF ELECTRIC WELDING 209 

K.v.a. means kilovolt amperes, or volts x amperes -h 1,000. In 
any inductive apparatus, such as a motor or welding machine, a 
counter current is set up within the apparatus itself. This makes 
it necessary for the generator to produce not only amperes enough 
to operate the motor or welding machine, but also enough in addition 
to overcome this opposing current, although the actual mechanical 
power required to run the generator is only that sufficient to supply 
watts or electrical energy (volts x amperes) actually consumed in the 
welding machine. Hence the k.w. demand of a welding machine 
represents the actual useful power consumed for which you pay, 
while the k.v.a. demand represents the volts x the total number 
of amperes impressed on the welding machine -5- 1,000, to overcome 
also the induced current set up within it. But it is the k.v.a. 
demand that governs the size of the wire to be used in the connecting 
up of the welding machine. K.w. divided by k.v.a. of any machine 
is usually expressed in percentage. 

According to a report submitted to the Convention of the Associa- 
tion of Railway Electrical Engineers, and reprinted in the Railway 
Review, December 2, 1916, ^--inch mild steel electrodes used for 
welding 2-inch flues require a current from 60 to 90 amperes, with 
a voltage from 14 to 16; 5-inch flues using a ^-inch mild steel 
electrode require a current of from 110 to 140 amperes, with a 
voltage of 16 to 20. Mild steel electrodes T % inch thick require 
a current of from 151 to 180 amperes, with voltage from 18 to 25 
volts. When carbon electrodes | inch thick are used for cutting, a 
current is needed of from 250 to 370 amperes, with a voltage of 35 to 
50 volts. In some outfits, however, carbon electrodes much smaller 
in diameter are used, one company employing only f^-inch diameter. 

When very thin sheet is welded with metallic electrodes with low 
current values. The following data for sheet metal are based on the 
cost of labour at Is. 6d. per hour, current at Id. per kilowatt-hour. 
Metal No. 20 gauge, metal electrodes T V-inch diameter, current 
10 to 25 amperes, speed 30 feet per hour, average cost f d. per foot. 
Metal 18-gauge, metal electrodes T Vinch diameter, current 35 to 
40 amperes, speed 28 feet per hour, average cost l|d. per foot. 
The cost of welding ^-inch thick plates by the arc welding method is 
about 50 per cent, of the cost of welding by oxy-acetylene on similar 
plates. To weld plates \ inch thick by arc welding will cost 40 per 
cent, less than oxy-acetylene. On 1-inch thick plates arc welding 
is 15 per cent, cheaper than oxy-acetylene, but the latter is better 
in regards to expansion owing to slow heating, which leaves small 
granular section. 

14 



210 MODERN METHODS OE WELDING 

The electric arc claims superiority over some of the other 
methods. First, the high temperature of the electric arc makes 
it possible to reduce rapidly to a molten state the metal to 
be welded. The heat being applied rapidly is not being carried 
away from the point of the weld by the heat conductivity 
of the metal fast enough to lower the temperature at the weld 
appreciably. Secondly, the tools for performing the weld are com- 
paratively easy to manipulate. The apparatus required is simpler 
than that used for gas outfits. Thirdly, for all work, except very thin 
materials, it is cheapest. Fourthly, the voltage of the current is so 
low that the process is perfectly safe. If the operator is provided 
with a proper hood or shield to protect him from the light and heat 
of the arc, he is not exposed to any danger. The heat and light from 
the carbon arc are much greater than that from a metallic arc. 

The greatest advantage of all, probably, is that the welds can 
be made overhead and on vertical seams by the metallic arc. The 
arc actually carries the metal particles from the electrode into the 
weld with considerable force, so that even with an overhead weld 
the metal is forced clear through the space between the adjoining 
surfaces, welding them securely. Overhead welding cannot be done 
so easily by any other means. The welds that are most commonly 
welded by the electric arc are mild steel, and steel castings. For mild 
rolled steel and steel castings, electrodes or filling rods of soft iron, 
preferably Swedish iron, are used. Tool steel may also be welded 
with Swedish iron electrodes. Copper has been welded to steel by 
using a copper-phosphor rod. Brass also can be welded with a 
brass-aluminium rod, bronze with a bronze-aluminium rod. 

It is not possible to weld aluminium, cast iron, or copper with 
much success, although attempts have been made. These metals 
are bssb lsf b to the oxy -acetylene process, with which a good weld 
can always be made. 



CHAPTER XXXIV 

ELECTRIC ARC WELDING 

Electric arc welding is a fusion process, and as is the case in the 
oxy-acetylene blowpipe system, the joint or weld is obtained by the 
autogenous union of the metal. The two pieces are united by 
filling new material between them, the electric current melting both 
faces to be welded, while at the same time the new metal of the elec- 
trode melts into the junction of the two. The quasi-arc process 
is dependent upon an entirely new phenomenon brought to light 
by investigation, and is so different in method and result from the 
arc fusion process that it merits being put in a class of its own. 
Not only is this new process much more rapid than any existing 
method, but it produces a perfect joint, owing to the fact that the 
heat introduced into the weld is automatically governed by the nature 
of the special electrodes employed. There is no limit to the size of 
the work which can be welded, no expensive plant or machinery is 
required, and the current consumption is extremely light. 

In this process the highly localised heating agency of the electric 
arc is employed to bring about autogenous union. The fusing 
starts immediately the arc is struck, but under such conditions 
that throughout the whole operation the fused adjacent metal is 
entirely protected from all oxidising influences. The result is 
obtained by the use of patented electrodes in conjunction with the 
patented method of application. The method of application is 
rendered possible by the special character of the covering employed 
for the electrodes, and eliminates the necessity for particular skill 
on the part of the operator, which is an essential feature of other fusion 
processes. Uniformly good and reliable results are obtained, and no 
appreciable thermal disturbance is caused to the structures of the 
surrounding metal. It is necessary, when preparing the weld, to 
have both edges of the line of welding bevelled if it is over ^ 3 T inches 
thick. 

The importance of forming a joint which shall contain no trace 
of oxide is so great as to deserve particular emphasis. Not only does 
the presence of oxide greatly reduce the strength of the weld, but 

211 



212 MODERN METHODS OF WELDING 

it renders the joint peculiarly liable to corrosion. But for the 
general welding in engineering works, shipyards, and steel foundries 
the only requisites, beyond the electrodes, are a simple electric 
holder, a supply of current, either direct or alternating, at a pressure 
of about 105 volts, and a suitable resistance for regulating the current. 
Should, however, direct current be available, this maybe used pro- 
vided that a reactance coil is installed in each welding circuit. 

The bared end of the electrode, held in a suitable holder, is 
connected to one pole of the current supply by means of a flexible 
cable, the return wire being connected to the work. In the case of 
small articles the work is laid on an iron plate or bench, to which the 
return wire is connected. Electrical contact is made by touching 
the work with the end of the electrode held vertically, thus allow- 
ing the current to pass and an arc to form. The electrode, still 
kept in contact with the work, is then dropped to an angle, where 
the arc is immediately destroyed, owing to the special covering 
passing into the igneous state, and as a secondary conductor main- 
taining electrical connection between the work and the metallic 
core of the electrode. The action once started, the electrode melts 
at a uniform rate, as long as it remains in contact, and leaves a 
seam of metal perfectly diffused into the work. The covering 
material of the electrode, acting as a slag, floats and spreads over 
the surface of the weld as it is formed. The fused metal, being 
entirely covered with the slag, is thereby completely protected from 
all risk of oxidisation. The slag covering is readily chipped or 
brushed off when the weld cools, leaving a bright, clean metallic 
surface. 

During the last two years much attention and investigation has 
been carried out on the problems involved in the application of 
the process to ship construction, with a view to the substitution in 
a large measure of quasi-arc electric welding for riveting. The 
investigation has been of a twofold character : firstly, by a series of 
exhaustive tests to determine the relative strength of quasi-arc 
welding under all conditions of stress and of various types of joints: 
and secondly, to determine what modification of design would be 
necessary or desirable where welding is adopted. The results of 
these tests, set out in the following pages, establish the fact that 
a Weld by this process is not merely as strong as, but is, in 
fact, substantially stronger than, a riveted joint, while the various 
modifications in design which have been evolved and patented 
by the Quasi-Arc Company effectually overcome many difficulties 
experienced in present practice in ship construction; and this, 



ELECTRIC ARC WELDING 213 

coupled with a notable saving in weight of steel used. Inasmuch, 
also, as the work of one welder is approximately equivalent to that 
of a squad of four riveters, there should be a substantial increase 
in the rate of joroduction, accompanied by econonw in total cost. 

In order to test the strength and suitability of a welded joint, 
it is not sufficient to be content with a mere tensile or bending test; 
a joint which could satisfactorily pass such tests might give a very 
poor result when an alternating or vibratory stress is applied — 
indeed, from the point of view of ship-designers, the latter is 
probably of greater importance than either of the former, and for 
this reason special attention has been given to the matter. The 
joints welded by different processes may give approximately equal 
tensile results, but show a marked difference when subjected to 
alternating stresses. Hence the importance of the adoption of such 
a process of electric welding, and electrodes of such standard 
quality, as will amount to a guarantee that a true crystal union 
actually takes place. 

The coatings may be of such a nature as to supply constituents 
that are burnt out in the metal in welding, and so compensate for 
their loss. In some electrodes aluminium wire is incorporated under 
the coating. Blue asbestos yarn is specially preferred as a coating 
for the electrode for welding mild steel and iron, as it is a reducing 
flux and may be smeared with a composition such as sodium silicate 
or aluminium silicate, to the very fusing temperature of the yarn. 
Extreme care is used in preparation of the electrodes, and much 
stress is laid on the good and regular quality of the metal of which 
they are composed, and upon the exactness and evenness of the 
coating. The metal electrode is positive to the work and, in fusing, 
is deposited upon it. The coating in melting forms a vitreous slag 
which covers the weld and flakes off more or less in cooling. The 
slag must be carefully removed if successive layers are required. 
The object is to protect the weld from absorbing oxygen and so 
avoid deterioration of the quality of the metal in the weld. The 
metallic electrode fuses into the joint prepared by bevelling the 
edges of the pieces to be welded, so that there is not properly an arc. 
The electrodes vary from 14 to 4 s.w.g. in diameter for ordinary 
work up to f-inch thick. The current is direct, and the voltage 
recommended is about 100, but much lower in amperes than 
with Bernodos' system, varying from 20 to 75 amperes according to 
the thickness operated upon. 

Cutting is impossible with a metallic electrode. The electrode 
melts away in the operation. If it touches the work it sticks to it. 



214 MODERN METHODS OF WELDING 

Occasional cooling by clipping the electrode in water is necessary. 
A carbon electrode is more easily manipulated for this purpose 
With the metallic electrode positive to the work, welds can be made 
upwards — that is to say, the operator can work underneath the 
article, and weld its under surface. This requires a particularly 
good operator. 

Many tests have been made, both in the laboratory and in 
practical service, and their utility has been fully demonstrated. 
The work, however, must be designed to suit the process, and the 
process must be regulated to suit the work, in order to attain 
success. 

Industry in wartime becomes founded on an entirely new 
process: production and speed of manufacture become of first 
importance; the cost becomes, to some extent, secondary. New 
methods must be introduced with a rapidity unknown in peace- 
times, and the taking of some chances becomes an absolute necessity. 
The desirability of avoiding machine work and of reducing to a 
minimum the labour item, the necessity of utilising unskilled labour 
wherever possible, all become of great importance. The necessity 
for long life is not always present; substitutes must be found for 
many materials where a shortage exists, and margins and factors 
of safety must be reconsidered and, wherever possible, reduced. 

The steel industry with its allied and auxiliary developments 
naturally becomes of first importance. The uses of iron and steel 
in wartime as well as in times of peace are so manifold as to pre- 
clude a detailed listing. In practically all the uses of steel several 
parts must be joined together to form a whole, and in many of these 
operations rivets have been the means of union employed. In the 
building of ships, in the construction of all structural material, 
wherever steel plate is used, and in places without number, the 
rivet has been the means of union between the two separate steel 
parts. In accordance with the law of economics, wherever a process 
can be performed in such a way as to show an advantage in quality, 
speed, cost, or quantity, it must supplant other methods. Electric 
welding, in some forms, gives every promise of replacing riveting in 
the enormous field which the latter has long held for its own. It is 
only when a rival appears upon the field that the characteristics 
and claims of a process are properly investigated. 

Electric welding is not a new art, but in its various forms has 
been used for many years. To those who have studied the subject, 
the possibilities of arc, spot, butt, and other forms of welding are 
well known. The results that can be obtained are matters of ex- 



ELECTRIC ARC WELDING 215 

perience, and years of actual service have sufficiently demonstrated 
the unquestionable reliability of the process. The careful and 
elaborate scientific investigations now under way to determine the 
characteristics and limitations of all the forms of electric welding 
vill soon place knowledge of the art on a broad basis comparable 
to that of our best engineering methods. The repair of the wilfully 
damaged German ships has been one of the most spectacular 
demonstrations of the possibility of the welding art. 

In those industries in which iron and steel parts are employed 
there is practically no limit to the opportunities for employing electric 
welding. In salvage and repair work it is being rapidly introduced. 
Ships, ships, and more ships was an urgent and familiar war cry, 
yet peace does not release us from building ships. In the course 
of a few years we may hope to see the electrically welded ship the 
rule instead of the exception. 

Arc welding is relatively slow, requiring more labour, but the 
apparatus is lighter and more portable. Electrodes for arc welding 
cost approximately 4d. to 6d. per pound bare, and from lOd. to 3s. 
per pound flux-covered. There is a wide range of chemical composi- 
tions, from almost pure iron and steel with high manganese, fairly 
high carbon. It is certain that, where the strength and ductility 
of a weld are important, thoroughly skilled operators are necessary, 
and these cannot be ordinarily produced with less than six or eight 
weeks' training. 

With the introduction of electric welding in shipbuilding 
comes the necessity of devising new methods of assembly and 
holding the plates in position for welding. Several methods have 
been proposed, but their success can only be demonstrated by actual 
experience. The author suggests a powerful magnet (such as one 
lifting iron plates in steel works) for holding the plates while they 
are tacked. This would save bolts and the need of bolting. The 
magnet could be moved from place to place by shutting off the 
current. Dependable arc-welded joints can be made with an 
average strength of over 90 per cent, of the plate strength, when 
backed up by butt straps with an average strength of over 100 per 
cent. Owing to the relative brittleness of arc-welded joints, much 
fear has been expressed as to their ability to withstand long-con- 
tinued vibration stresses and shocks. Welding affords the most 
simple and effective means of making joints in steel plates capable 
of holding, without leaks, the warm oil which the tanks contain 
in service. The use of welding has lowered the cost of tank- 
making very materially, and has reduced the amount of noise 



216 MODERN METHODS OF WELDING 

in the tank-shops, thus making the tank-maker's job more 
agreeable. 

The apparatus required for electric welding is comparatively 
simple and very durable. When once it is installed, the operator 
requires only his electrodes, and a source of electrical energy. 
A successful operator must be a man of honest temperament, con- 
scientious, and interested to obtain the best results. He may be 
taught in a few days to hold the arc steady ; in about three months 
he may become an average operator. It requires some time to 
acquire the skill necessary to produce fairly uniform results in the 
different positions in which welding must be done. The operator 
must acquaint himself with the flow of the metal, in order to know 
definitely whether the current which has been selected for welding 
is too high or too low; he must come to know if the plates being 
welded are penetrated enough with the arc to form a good joint; he 
must observe the movement and the condition of his work, so that 
he can leave the least possible strain in the completed weld. These 
and many other points are to be learned principally through 
experience. 

Preparation o£ the Work for Welding. 

It is essential that the work be properly prepared before welding 
is begun. A thorough study must be given to the job in hand before 
anjr attempt is made to weld. This study must be first applied to 
the effect of heat on the parts to be joined; secondly, to the accessi- 
bility of the parts to be welded; thirdly, to the nature of the strains 
to which the weld will be subjected; fourthly, to the cleaning and 
assembling of the parts; fifthly, to the position in which the weld 
can be made; and sixthly, in what condition the weld is to be left 
when finished. 

(1) The effect of heat is to produce expansions and contractions 
which must be provided for wherever possible, otherwise severe 
strains may be left in the plates and welds that will materially reduce 
their effective strength or leave the work in a warped and distorted 
condition. 

(2) The parts to be welded should be made accessible, so that the 
welding may be performed thoroughly and the work of the operator 
simplified. 

(3) A study of the strains to which the work will be subjected 
is necessary in order to determine the kind of weld that should be 
used. Different kinds of welds will be required according as the 
strain is a direct tension, bending, torsion, prying, compressive, or 



ELECTRIC ARC WELDING 



21', 



a composite one ; and as the strength must be great, as in a main 
seam, or small, as in a caulking weld. 

(4) The cleaning and assembly of parts must be such as to pro- 
vide clean, proper, and sufficient contact surface for the welded-in 
portion, and so arranged that a good and substantial joint will 
result. 

(5) Wherever possible, the joint to be welded should be placed in 




Fig. 107. — Use of Metal Electrode in Welding Steel Bands to Pressed 

Corrugations. 



a position which will be the least arduous for the welder. Under this 
condition he will naturally do his best. Such a position is usually 
in the horizontal plane. Vertical and overhead welding may be 
done, and done well, but these positions are more difficult and tire- 
some for the welder. 

(6) Usually the " welt," or raised portion of the weld, is left on. 
But it is sometimes necessary to remove this and have a plane sur- 
face; for example, round the top of a tank which is to have a special 



218 MODERN METHODS OF WELDING 

finish the entire raised portion of the weld may be removed. Under 
these conditions a light reinforcing weld may be made on the seam 
inside the tank to compensate for the metal that has been removed . 
It is important, if the weld is to be made continuously in one layer, 
to allow for a contraction of the joint as the weld progresses. Unless 
this is done, undue warping and excessive internal strains may 
result. The amount of this contraction varies slightly with the 




Fig. 108. — Use of Carbon Electrode with Metal Filler when Welding 
]--Inch Thick Steel Base to the Edges of Pressed Corrugations. 

speed at which the work is done, and is about 1 1 per cent, of the length 
of the weld. Clamps are used to hold the plates the proper distance 
apart, and these are gradually released as the weld approaches 
them. The operator watches the opening. If it closes too quickly, 
he hurries his welding. If it does not close quickly enough, he waits 
for it. These precautions need not be taken in very short butt 
welds. Such welds are too short to develop any serious strains. 



ELECTRIC ARC WELDING 



219 



Welding with Metallic Electrodes. 

Many of the accompanying illustrations show samples of metallic 
electrodes welding work in tank-manufacture. These indicate that 
a' great variety of work can ably be done by arc welding with 
metal electrodes, and show that such operations are thoroughly 
practicable, and the results neat and substantial. 




Fig. 109. — Seam Prepared for Hand Welding with Carbon Electrode asu 
Operator in Position for Welding. 



Welding with Carbon Electrode. 

The method applied to light corrugated tanks differs from those 
used on boiler plate tanks. The sheet steel of these corrugated 
tanks is principally of T V and 4\ inch thick and the carbon 
electrode is used primarily to fuse together the upturned edges 
of the sheets. The carbon electrode is also used in conjunction 
with a metal filler when placing the |-inch bottoms in the corru- 
gated tanks. The metal electrode, also, is used on these tanks 
when welding the band to the corrugations. Welding, as applied 
to corrugated construction, is graphically portrayed in the illus- 
trations of these tanks. 



220 



MODERN METHODS OF WELDING 



Electrodes. 

The bare electrodes that have been found satisfactory for tank 
construction are as follows : 

(1) Norway or Swedish iron. 

(2) Toncan iron. 

(3) Armco bright hard-drawn electric welding wire. 
(•!) Roebling bright hard-drawn electric welding wire. 

These wires and the tank steel have the following analyses : 





Steel Plate. 




Sted W 


ire. 








1 


2 


3 


4 


Carbon per cent. 


0-25 


0-049 


0-10 


0-078 


0-185 


Manganese ,, 


0-40 


0-021 


0-16 


0-041 


0-561 


Phosphorus ,, 


0-025 


0-025 


0-025 


0-010 


0-032 


Silicon ,, 


0-000 


0-08 


trace 


0-000 


trace 


Sulphur ,, 


0-028 


0-08007 


0-046 


0-032 


0-038 



A satisfactory welding wire will melt and drop small particles 
uniformly into the weld. 

If there is considerable spluttering, and large globules drop from 
the welding-rod, the weld will be very porous, and the deposited 
metal will be poorly united to the plates being joined. 

It is difficult to give universally applicable figures covering 
amperes, speed, etc., for electric welding, owing to the effect of 
conditions under which the work is done, the character of the work, 
and, to a very large extent, the skill of the operator. The following 
figures are based on favourable working conditions and a skilled 
operator. They are approximations only, and are given merely as a 
general guide. 



Metallic Electrode Welding. 



Electrode Diameter in 
Inches. 



Amperes. 



i 


25 to 50 


a 

ITT 


50 „ 90 


* 


80 „ 150 


5 


125 „ 200 


.1 
TS 


175 „ 225 



Corresponding Plate 
Thickness in Inches. 



up to T s ¥ 



itol 



f and up 



The same size electrode may be used with various thicknesses of 
plate. The heavier plates will require heavier currents. Approxi- 



ELECTRIC ARC WELDING 



221 



mate speeds of welding sheet metal with metallic electrodes and 
oxy-acetylene welding are given in the f ollowing table : 



Thickness of 
Plate. 


Speed, Feet per 
Hour. 


Cost per Foot 

of Electric Arc 

Welding. 


Comparative Cost 
per Foot of 
Acetylene. 


i 

IF 




20 


2-12 


1-78 


X 




16 


3-12 


4-66 


l 




10 


7-13 


12-3 


_3_ 




6-5 


12-3 


36-1 


1 




4-3 


19-8 


much, higher 


a 




2 


41-7 


;s 


1 




1-4 


61-3 


" 



Any direct source can be used for welding, but the voltage of the 
arc must be reduced to values of from 50 to 20. The G.E.C. have 




Pig. 110. — Complete Unit eor Electric Arc Welding. 

developed a special line of low-voltage generators and controls, 
which give a very good efficiency, combined with flexibility and 
ample protection. The generator is wound for a voltage of 60 to 
75. In no case is it necessary to have a generator of higher voltage 
than this. Lower voltages may occasionally be used with low circuit 
values. The generators are usually furnished as a part of a motor- 
generator set, although they can be supplied for a belt drive if 
desired. The motor-generator set is the most desirable equipment 
for several reasons : it is a self-contained unit and does not demand 
any attention when running; the maintenance is low; the weld- 



222 



MODERN METHODS OF WELDING 



ing circuits and the shop circuits are electrically independent, so 
that short circuits in the welding circuit will not seriously interfere 
Avith the shop circuit; the voltage on the welding circuit can be 
regulated, if desired, by adjustment of the generator field rheostat. 
The control equipment consists of a main generator panel, with or 
without a welding control circuit, with a separate auxiliary panel 
for each operator. The equipment mounted on these panels is 
shown herewith. In addition, there is, in series with the arc, a grid 
rheostat for varying the current by means of 
a dial-switch shown on the panel. 

The automatic control equipment gives 
thorough protection to the generator without 
affecting other operators whose welding cir- 
cuits may be connected to the same generator ; 
this equipment consists of a protective relay 
controlling a shunt contactor in the welding 
circuit. The setting of the dial-switch on the 
welding panel determines the amount of re- 
sistance in series with the arc, and therefore 
controls the current used. This is regulated 
by the current required by work done. -Before 
starting the arc the operator must set the 
dial-switch for the amount of current required, 
so that on starting the circuits are in noimal 
running position. There is no necessity for 
having any relays or switches open or closed, 
or in any way changing or disturbing the 
electrical circuit in order to weld. 

Where welding by the carbon electrode is 

to be done, thin metal can be welded using 

150 to 250 amperes. Medium welding by this 

process requires from 250 to 350 amperes. 

Heavy welding will require 400 to 600 amperes. 

Where cutting is to be done by the carbon 

arc, the capacity of the set depends on the 

cutting speed required. For light metal where 

speed is not important, 300 amperes are sufficient, but where the 

metal is 2 inches thick or more it is desirable to use heavier 

currents. For this purpose up to 1,000 amperes can be used. 

In addition to the equipment and accessories previously described, 
special jobs render it desirable to have on hand other miscellaneous 
pieces of equipment. Odd pieces of copper and carbon blocks are 




Fig. 



111. — Welding 
Panel. 



Setting of the dial-switch 
determines the amount 
of resistance in series 
with the arc. 



ELECTRIC ARC WELDING 223 

of much assistance as " dams" in holding the metal in place. In 
cases where the weld must be smooth on one side, a piece of copper 
or carbon is held against the weld, and the metal filled against it. 
Iron and steel can be used if care is taken not to weld it. In filling 
a hole, the bottom is often closed by holding a plate of copper or 
carbon against it until sufficient is filled in. Care should be taken 
to flow the molten metal against the guide-pieces, not to allow the 
arc to play directly on them. Otherwise the weld will probably be- 
come contaminated by this material, or else the guide-pieces may 
be welded solid and not easily removed. A steel wire scratch-brush 
is used to remove slight scale and rust before commencing the weld, 
also at intervals during welding — -as when changing electrodes. 
For small work the positive lead may be bolted to an iron plate, 
forming the top of a work-bench. The work may be set on this 
bench, the contact being sufficient to carry the current. In many 
cases a vice mounted on the table will be found useful. 

If the work is too large for the table it may be set beside the 
table and a bar laid across it. This will provide sufficient current 
carrying capacity, providing that scale and rust do not prevent 
contact. A convenient terminal for the positive cable consists of 
a copper hook of proper size, to which the cable is bolted. If weld- 
ing is to be done in a room where other employees are doing different 
work, screens should be provided around the welding operator. 
They should be high enough to prevent the light striking a large 
part of the ceiling, since the flicker of this light would probably 
affect other workmen. The effect, while probably not injurious, 
would be irritating. White walls and ceilings should be avoided 
in a welding room. Gas-burners or annealing furnaces for pre- 
heating fire-bricks, sand, or asbestos sheeting for covering are useful, 
especially in cast-ironwork, which in many cases should be preheated 
uniformly to a red heat and welded at that temperature. A recep- 
tacle of water is desirable in which the electrode holder can be cooled 
when it becomes too hot after continual use. 

Some operators feel that gloves are necessary to protect the hands 
from the arc. In many cases, however, the operator finds gloves 
to be in the way, especially when working with a metallic electrode. 
If desired, however, any leather glove will give sufficient protection 
to the skin of the hands, which is much less sensitive than the skin on 
the other parts of the body. The arms, face, and neck should, how- 
ever, be covered, since exposure of these parts will probably result 
in burns similar to sunburn, which, while not serious, are painful. 

Flux. — It is the experience of a great majority of operators that 



224 MODERN METHODS OF WELDING 

flux of any kind is unnecessary in welding. Further, that it is a 
source of danger, in that there is liability of contaminating the 
weld. If the work is kept clean by brushing at equal intervals, 
and ordinary care taken in the operation of the arc, a good weld 
can be made without flux. If these precautions are lacking, flux 
will not make a good weld. 

Preparation of Welds. — Metal that is clean is much more likely 
to make a good strong weld. Scale, rust, grease, soot, and any foreign 
matter will contaminate the weld. Such inclusions necessarily 
weaken it, or else make it hard. Impurities may also make the 
metal porous and spongy, owing to the liberation of the gases. 
Pieces of foreign matter may prevent the molten metal from filling 
all the parts of the weld and cause cavities. Various methods of 
cleaning are in use: pickling for small parts, washing with petrol 
or lye, boiling with lye and sand, sand-blasting, chiselling, scratch - 
brushing, etc. — the method depending on the local conditions. 
Preparatory to welding locomotive tubes to the sheets, it is sometimes 
advantageous to send the locomotive out for a run to burn off the 
grease, and then clean off the oxide and sootby sand-blasting. Another 
method is to heat the boiler to normal by steam pressure, and then 
to clean by sand-blasting or scratch-brushing. Washing with lye 
will also remove the grease. In welding heavy sections, where it is 
necessary to deposit several layers of metal on the surface, the 
preceding layer should always be cleaned before starting the next. 

Sections of §■ inch or less in thickness need not be bevelled, but 
they should be separated about -J inch. Thicker sections should 
be bevelled to give a total angle of 60° as well as separated |- inch. 
In some special cases angles as low as 40° may be necessary, while 
as high as 90° may be used; but an average and safe value is 
60°. Still heavier sections may be bevelled both sides and the weld 
made from both sides. 

In the latter case a layer should be put on one side, then a layer 
on the other, to prevent warping ; for long seams the edges should be 
kept about |- per cent, apart, at the opposite end to which the 
welding is started; at the end where the weld starts this is to be 
kept open | inch. This takes some of the expansion and contrac- 
tion of the metal in the sheet. Another method of reducing 
contraction is to put in short sections at intervals, welding in 
one layer at a time, starting at the centre and working altern- 
ately to each end. Then put a layer on the open sections, and 
continue in the same way until the weld is complete, the welded 
section of any layer below or above the joints being broken 



ELECTRIC ARC WELDING 225 

as in laying brickwork. Still another method: instead of be- 
ginning the weld at the edge of the plate, start it some distance in 
and weld towards the edge of the plate. Then a second weld is 
started the same distance ahead of the first section. This method 
is called back- welding. The length of each section depends on the 
total length and may vary from 4 to 10 inches. In the welding of 
complicated shapes, such as flywheels, some castings may require 
preheating at certain points to produce initial expansion, which will 
be overcome as the weld cools. In some cases the entire pieces must 
be preheated; in others, after welding, -the whole piece must be 
annealed. This is done by heating the pieces uniformly, then cover- 
ing it with sand, asbestos, etc., and allowing it to cool slowly. In 
welding cracks in plates, forgings, or castings, the crack or fracture 
should be bevelled entirely through within -jV inch of the bottom. 

In boiler work |-inch holes are sometimes drilled just beyond the 
crack to prevent further fracture. 

Welding with the Metallic Electrode. — The arc should be kept 
short, not over |- inch in length. The current should not be greater 
than that indicated in the table for the electrode. Excessive current 
burnt or porous metal to be deposited. The arc should be kept 
constant in length to ensure uniformity in the metal deposited. In 
welding a seam the electrode should be moved with a zigzag or gyra- 
tory motion: the motion must be an advancing one along the seam. 
The metal will adhere only to the surface of the work actually played 
on by the arc, so care must be taken to bring the arc in contact with 
the whole surface to be welded. Be sure that the electrode is con- 
nects! to the negative terminal. If the polarity is reversed the 
arc will be more difficult to maintain, the electrode will not be as 
good as it should be. In starting the arc, the electrode should be 
just touched to the work, and withdrawn immediately to the required 
distance. If the electrode is held too long in contact it will not work ; 
in this case the relay, if adjusted properly, will operate opening the 
circuit, after which the electrode can be knocked loose. 

In welding, be sure that the arc plays over the entire surface of 
the joint. The metal of the work is fused by direct impact of the 
arc ; if the molten metal merely runs ahead of the arc, over the solid 
metal of the work, it will not result in a weld. The metallic electrode 
used is generally from 14 to 18 inches long. It may be gripped in the 
holder, either at one end or in the middle as required by skill of the 
operator or the nature of the work. The operation of welding over- 
head is the same as in normal welding. The difficulty largely lies 
in the holding of the electrode steady in the cramped position 



226 MODERN METHODS OF WELDING 

usually required. If the arc length is kept constant the metal will 
be successfully deposited; practice is required to accomplish this. 
The appearance of an over weld is sometimes marred by drops of 
metal projecting, or by uneven thickness of the deposited metal, 
but this can be overcome by proper manipulation of the electrode. 
A rest for the arm will sometimes assist the operator to hold the 
electrode steady. 

The Use of the Carbon Electrode. — -The holder should grip the 
electrode from 4 to 5 inches from the end, the electrode for ordinary 
work to be tapered to a blunt point at the working end. These 
carbon electrodes are specially made from a superior grade of pure 
graphite. They are stocked in three sizes — f inch, -| inch, and 
| inch diameter — and 12 to 24 inches long. To deposit metal 
with the carbon electrode, the arc is struck as above, but it 
is not held long enough in one place to melt through. A pool 
of molten metal is established, a melting-rod of metal is fed 
into the arc melted down in the work. It should all be heated 
thoroughly to ensure complete union before more metal is added. 
Since a heavier current can be used with the carbon electrode 
than with fehe metallic, faster work can be done in depositing 
metal. The quality of the weld is not quite so good, however, as 
when the metallic electrode is used. However, for filling holes in 
castings,burning up worn spots, etc., the carbon weld is satisfactory 
and should be used. Owing to the temperature and the large 
amount of heat liberated when using the carbon electrode, the elec- 
trode holder is liable to become very hot, and, under some conditions, 
melt away at the end. When the holder begins to get hot it should 
be plunged in the receptacle of water kept conveniently near the 
operator. 



CHAPTER XXXV 
SPOT WELDING 

Spot electric welding is the process whereby two pieces of metal 
are united by heating until they reach a semi-molten or plastic 
stage, when they can easily be forced to cohere or weld by the appli- 
cation of pressure. The complete cohesion of the heated molecules 
makes the two pieces of metal practically solid where they are 
forced together. It is necessary that the area to be welded should, 
at the start, be brought into more intimate contact than the sur- 
rounding areas, in order that the current may be properly localised, 
and the heat generated in the region where it is needed. 

Some of the advantages of spot welding are that the weld is 
softened or changed in its texture after welding by the application 
of considerable heat, and for this reason it can be extensively used 
in the manufacture of stoves or other articles subject to high heat, 
where even brazing could not stand up. There is no noise in con- 
nection with the operation, no dirt, smoke, or wasted heat. The 
current is only on for a brief period of the time required to heat the 
two sheets of metal at the point of the weld, and as soon as the 
welding is completed all expense of current ceases immediately. 
Owing to the way the metal is forced together, no oxidation can take 
place on the abutting surfaces; therefore, no welding compound 
or deoxidiser of any kind is necessary. First the stock must be 
cold rolled, hot pickled, or sand-blasted to remove all scale or dirt, 
which acts as an insulator and cuts down the capacity of any spot- 
welding machine. The welding machine is always ready to make 
a joint at the will of the operator ; yet, as soon as the welding has 
been completed, the machine is practically dead, and the current 
expense is stopped until the next operation. The metal is in full 
view of the operator at all times, and no smoked glasses or goggles 
are required. 

The sheets to be welded must be perfectly flat and in good con- 
tact at the surface to be welded, so that no great mechanical pres- 
sure is required to flatten down any bulges or dents to bring the two 
plates of stock into good contact directly under the die-points. 

227 



228 MODERN METHODS OF WELDING 

The stock must not surround the lower horn in any way like a 
cylinder or a rectangular box, as would be the case in welding the 
seam-side of a can or pipe. These conditions are not to be interpreted 
as meaning that no spot welding can be done unless they are abso- 
lutely followed, but merely to give a basis on which the ratings are 
calculated. If any of these conditions are violated — which is often 
necessary, especially the last one — it will still be possible to spot 
weld, but the capacity of the machine will be cut down. The cut- 
down of the capacity as outlined (by the stock not surrounding the 
lower horn) is due to the self-induction effect of the metal, which 
tends to choke back the main current and in this way cuts down 
the welding effect at the die-points. This is lost energy, as the 
amount of current choked back is not used in any way. 

The theory of this choking back would be too lengthy to explain 
in full, but, to give a brief analogy, it might be compared to the back- 
pressure effect on a petrol engine in a motor-boat, where the ex- 
haust is located under water and the power of the engine is reduced 
owing to the back-pressure caused by the water pushing against 
the exhaust gases. This induction effect, so called, is only present 
in welding iron and steel, no such effect being experienced with 
brass. 

Light gauges of sheet metal can be welded to heavy gauges or 
solid bars of steel if the light metal is not greater than the rated 
single sheet capacity of the machine. Soft steel and iron form the 
best welding materials in sheet metals, although it is possible also 
to weld sheet iron or steel to malleable iron castings of a good 
quality. Galvanised iron can also be welded successfully, although 
it takes a slightly longer time than clear iron and steel stock in 
order to burn off the zinc coating before the weld can be made. 
Contrary to common opinion, the metal at the point of the weld 
is not made susceptible to rust by burning of this zinc, since by some 
electro-chemical action it has been found that the spots directly 
under each die-point and also around the point of the weld between 
the sheets are covered with a thin volume of zinc oxide after the 
weld has taken place, which acts also as a rust-preventative to a 
very noticeable degree. 

On spot-welded articles used in practice for some time, such as 
galvanised road culverts, refrigerator-racks and pans, rain gutters, 
buckets, etc., it has been found that no trace of rust has appeared on 
the spot welds from their exposure to ordinary conditions. Extra 
light gauges of galvanised iron below No. 28 B. and S. cannot be 
successfully welded, owing to the fact that so little of the iron is left 



SPOT WELDING 229 

after the zinc has been burnt off that the metal is very apt to burn 
through and leave a hole through the sheets. Tinned sheet iron 
or steel makes an ideal metal, giving great strength at the weld, 
but the stock will be discoloured at this point over the area covered 
by the die-point in operation. Sheet brass can be welded to brass 
or steel if it contains not more than 60 per cent, copper. It is not 
practicable to attemptto weld any bronze or alloy containing a higher 
percentage of copper than this, as no great strength can be obtained 
Another class of work which can be handled to good advantage on 
a spot-welder, although it is not strictly spot welding, is the con- 
struction of wire- work articles. 

This mesh welding of two crossed wires is usually done with the 
same two copper dies as are used for spot welding, except that the 
dies are usually grooved in order to hold the wire in the desired 
position to weld. The welding itself is quite as rapid as that of 
sheet metal, but a jig to hold the wire parts together in the correct 
position before welding the joint is usually required in order 
to secure high production. Among common wire-work articles 
assembled by this method of welding will be found lamp-shade 
frames, oven racks, dish strainers, waste baskets, etc. 

Spot welding requires as part of its equipment a suitable trans- 
former. The essentials for the purpose are : 

(1) Very large currents at low voltages, the currents running as 
high as 50,000 to 75,000 amperes, the voltage 4 to 15. 

(2) Different classes or thicknesses of metal having to be welded 
by the same outfit, it is necessary to provide variation in voltage in 
order to obtain suitable currents for the different classes of work. 

(3) On account of high current it is necessary to have the trans- 
formers as near the work as possible to avoid excessive cost of low 
voltage bus bars. 

(4) The fact that the transformer is an integral part of the weld- 
ing machine, and as such may be subject to very rough usage in 
factories, blacksmiths' and boiler shops, etc., or may even be ex- 
posed to the weather, necessitates particularly rugged construction. 

Spot welding is the method of joining metal sheets together at any 
desired point by a spot, the size of a rivet, without punching holes 
or using rivets. It is done electrically by fusing or melting the metal 
at the point desired, at the same instant applying sufficient pressure 
to force the particles of molten metal together. The theory is as 
simple as its application. It is a well-known principle that a poor 
conductor of electricity will offer so much resistance to the flow 
of the current that it will heat, the degree of heat depending on the 



230 



MODERN METHODS OE WELDING 



amount of current and the resistance of the conductor. Copper 
conductors carry the current with very little resistance. Place a 
piece of iron in the circuit ; it is not so good a conductor as the copper, 
and will heat. If the volume of the current is large, and the iron 
conductor much smaller in diameter than copper, the iron will 




Fig. 112. — Prescot Spot Welder. 



quickly become hot enough to melt. An incandescent lamp offers 
a good illustration of this principle : the copper wires leading to 
the lamp are good conductors and remain cool; the carbon fila- 
ment, being a poor conductor, becomes white-hot, and reaches a state 
of incandescence. 



SPOT WELDING 



231 



Instruction for Working the Machine. 

Set the regular handle to the extreme left-hand side, No. 1, 
and the double-pole, double-throw switch to the left. Place the 
work between the copper die-points and close the dies on the work. 




Fig. 113. — This is a Specially Good Sample: First, Three Flat Bars to 
Corrugated Sheet; Second, a Flat Plate Welded to the Flat Bars 
and Plate; Fourth, Bent Flat Bars Welded to Corrugated Sheet, 
Flat Bars, Plate, through All Pieces. 

This will force the stock together. The current is turned on with 
the switch. If the stock does not heat rapidly enough, turn the 
regulator-handle to the right, or No. 2. If not enough is obtained 
at this point, keep on until the point is reached; if enough heat is 




Fig. 114. — One Piece op Angle Iron to Flat Plate. Two Spots. 



not obtained, throw the double-pole switch to the right, and the 
lever handle to No. 1. The maximum current is obtained when the 
regulator is at the right. 

There is absolutely no danger of getting a shock on the machine 
between the upper and lower dies, as can readily be proved by plac- 



232 



MODERN METHODS OF WELDING 



ing the fingers through from the upper to the contact points and 
turning on the currents. 

The voltage is so low that it is impossible to feel anything. Do 
not touch the wires leading from the transformer or dynamo to the 
machine without first opening the switch on the wall. There is no 
occasion for the operator to touch these wires in any way after the 
machine has been connected up. 

Figs. 113, 114, and 115 are samples of spot welding. 

There is a limit to the thickness of sheet metal which it is 
commercially practicable to spot weld, owing to two causes: 

First, the fact that the copper rods which conduct the electric 
current can only carry a certain quantity of current without exces- 
sive heating. When sufficient current is carried over these copper 
rods or die-points to bring the heavy bodies of metal up to the weld- 




Fig. 115.- 



-Three Pieces of Round Iron Welded to an Angle Iron. 
Good Test. 



ing temperature, the copper rods will become hot ; then they soften, 
and the points will wear away quite rapidly. 

Secondly, it being necessary to have two pieces of sheet steel 
touching each other at the point where the weld is made, with very 
heavy stock a slight kink or buckling of the metal will prevent the 
flat surfaces from touching each other and making good contact. 
Light gauges of sheet steel can be welded to heavy gauges or to solid 
bars of steel. It is not possible to weld two pieces of cast iron, owing 
to the crystalline structure of the metal. Sheet steel can be welded 
to cast iron, but can easily be pulled apart. The sheet tears out 
small particles of cast iron. Galvanised iron can be welded, although 
it will burn off the zinc somewhat where the weld is made. The 
author does not advise the welding of light galvanised iron above 
24-gauge, as there is no body of metal to work on. By the time the 
weld is done the zinc is burnt off and there is nothing left. Sheet 
brass can be welded to sheet brass or sheet steel. There is a little 



SPOT WELDING 233 

knack in welding work of this kind, and it may take a bit of experi- 
menting to get the right heat and pressure. 

Some grades of sheet aluminium can be spot welded, although it 
will leave a slightly roughened surface where the die-points come 
together. It is more difficult to weld sheet copper to sheet copper, 
as this metal is such a good conductor of the electric current that 
there is practically no resistance offered by the metal. Rivets of 
any size can be heated after the rivet has been set in the rivet- 
hole, and headed and pressed in place at one operation by use of the 
welder. This process can be used to advantage in many cases. 
Heat has no effect on the electric weld. For this reason the process 
is largely used by stove manufacturers in making sheet-steel ranges, 
and for similar work. 

To facilitate the welding of awkwardly shaped articles the bottom 
stake may be swivelled and raised or lowered. With such a com- 
bination it is practicable so to arrange the stakes that the most 
awkwardly shaped articles can be handled. The welder is foot- 
operated, and no skilled labour is required. Foot pressure on the 
pedal brings down the top electrode towards the bottom electrode, 
pinching between them the articles to be welded, which are held 
there by the operator. The same downward movement of the pedal 
switches on the welding current. After welding temperature is 
reached — judged by the colour — further pressure on the pedal trips 
the switch and applies pressure to force the heated metal into 
welding. The pedal is made reversible, so that the welder may be 
operated by either right or left foot. The tips are made of copper 
and are water-cooled, with a constant flow of water. The system 
of c'ooling is so efficient that the tips may be touched by hand 
immediately after welding. Usually the tips last for a few weeks' 
constant use. They are easily and cheaply replaced. 

Operating Instructions. — Select the pieces to be united, range 
them together in the required position, just as they will be when 
welded, and clamp them thus between the electrode tips. This is 
done by holding the pieces on the bottom electrode until the top elec- 
trode has been brought down by depressing the foot-lever. Directly 
the pieces are clamped between the electrodes, they become white- 
hot at the points where the electrode tips make contact; and the 
pressure between the surfaces, maintained by the foot-pedal, forces 
the metal to unite and forms a weld. The metal should be as free 
as passible from rust, scale, dirt, or other foreign matter likely to 
hinder the passage of the welding current. No preparation is neces^ 
sary unless the metal is very dirty, in which case it will be economical 



234 MODERN METHODS OF WELDING 

to clean it, since less current will be required. The time taken to 
weld varies from a fraction of a second to perhaps one second. No 
definite rule can be given that will decide all cases. It depends on 
the thickness of the metal, its freedom from dirt, the position of the 
plug in the plug-box, and the diameter of the spot weld made. 
A few hours' experimenting is generally sufficient to teach the average 
operator. The plug should be in No. 1 hole when welding the 
thickest material, in No. 4 for the thinnest. The shape of the elec 
trode tip decides the diameter of the spot. If a small spot be 
required, the tips must be reduced at the tip ; if a larger spot, the 
tips must be flattened. 

Adjustments, Tips. — The electrode tips will require to be filed 
from time to time, to remove any metal which may adhere to them. 
Each tip is quite easily removable after loosening with a spanner. 
Care should be taken not to turn the tip completely round, as one 
would a nut. Just move it from left to right a few times, when it will 
be loosened and may easily be removed. 

Three types of electrode tips are made : 

(1) Concentric — -that is, with welding point exactly in the middle 
of the electrode. 

(2) Eccentric — that is, the welding point a little out of centre. 

(3) Flat — that is, no welding point at all. 

The concentric type is most often used, but it demands a maxi- 
mum amount of clearance around the weld. For welding in corners 
and places where there is little room, the eccentric is used. The 
flat type may be used with either a concentric or eccentric tip, but 
it is only used when it is desired to avoid, on one side, the little 
indentation made by the pointed electrodes. All these tips are 
interchangeable, suitable for either top or bottom stakes. 

Pressure while Welding. — One of the most important points to 
remember is the necessity of having a fair pressure between the sur- 
faces to be welded before the current is switched on by closing the 
switch at the back of the welder. This can easily be arranged for 
by moving the top or bridge of the switch up and down the rod on 
which it is mounted, adjusting so that the electrode tips are forced 
well together before the switch closes. Care must be taken to 
see that the electrode tips are directly in line when touching. If 
one is a little to the side of the other, the weld is likely to be burnt. 
Directly the article to be welded is clamped between the electrodes, 
the secondary circuit is closed, but no current flows until sufficient 
pressure has been set up by the foot-pedal to close the primary switch 
at the back of the welder. Closing the secondary circuit before the 



SPOT WELDING 235 

primary ensures a steady flow of current through the point of the 
weld, free from sparking. 

Switch. — This is fitted at the back of the welder and should be 
inspected from time to time to ensure the points of contact being 
kept clean. 

Hinge. — To permit the top arm to move down easily when the 
foot-pedal is depressed, while yet maintaining good electrical con- 
tact, it is carried in a special hinge. The arm rocks up and down 
on ball-bearings, and electrical contact is ensured by two discs, 
which are a sliding fit in the secondary casting, and are pressed up 
against the top arm by the springs under the nut-washers on each 
side. These nuts may require tightening from time to time, so as 
to keep the contact discs in close contact with the top arm. Great 
care must be taken not to make them too tight, or excessive friction 
will be set up and the faces will be scored. No lubricant must be 
used. Should the faces at any time become scored, take the hinge 
apart, smooth the faces, and polish with metal polish. The ball- 
bearings require no attention. 



CHAPTER XXXVI 
ELECTRIC BUTT WELDING 

Electric butt welding is a process wherein two pieces of metal are 
united by the cohesion of their molecules, induced by the application 
of pressure when they are in a plastic or molten stage through being 
heated by some process. In the process of electric welding the heat 
is induced by passing a large volume of electric current at a low 
pressure through the two surfaces of the pieces to be welded, the 
heating effect in any electrical circuit being evoked by the resistance 
of the metal to the flow of the current. When the point between 
the abutting ends, which has the highest resistance in the circuit 
and therefore the highest heat, has reached the proper welding 
temperature, the current is turned off and the pressure applied 
mechanically to force the molten ends together, thereby producing 
a weld. 

Butt-welding machines are designed for the manufacturer who 
has a large quantity of this kind of work to do, where there are many 
pieces of one kind to weld. They are not intended to replace the 
blacksmith for general repair work where there are a few pieces 
of various sizes to be welded. It is purely a production proposition 
for a volume of work with a minimum of cost. 

In butt welding the two pieces of metal are placed in the clamp- 
ing jaws of the machine with a proportion of the ends extending 
beyond the jaws. The electric current is turned on by means of a 
switch, and the abutting ends of the metal instantly begin to heat. 
The operator quickly learns to judge by observation when the weld- 
ing temperature is reached. When he sees that the metal is hot 
enough, he applies the pressure and forces the two metal ends of the 
pieces into each other, at the same time turning off the current, and 
the weld is made. The metal is in full view of the operator all the 
time, instead of being hidden by the coal and flame in a forge fire. 
No smoked glasses or goggles are needed any more than they are by 
the blacksmith. There is no scarfing to be done, and owing to the 
way the metal is forced together, there is no oxidation such as there 
would be in the open fire. Consequently, no welding compound is 
necessary. In a forge fire a thin film of oxide forms on the metal, 

236 



ELECTRIC BUTT WELDING 237 

which must be removed by a welding compound from the two sur- 
faces to be joined before a good weld can be made. 

With electric welds the heat is first develoj)ed in the centre of 
the metal. In consequence, it is welded there as perfectly as the 
surface. When welding electrically, little energy or heat is wasted 
in heating more of the material on either side of the weld. The 
operator has complete control of the electric current by means of his 
current regulator and switch. He can quickly obtain any heat 
desired, from a dull red to the melting-point of the metal. The 
instant the weld is made the expense for current stops. Owing to 
the low voltage employed across the work itself there is not the 
slightest danger of injury to the operator. He cannot even feel the 
current if he should come in contact with it across the dies. The 
parts to be welded can be kept in fairly close alignment by the 
clamping of the jaws, which can be given almost any shape desired 
to hold the work. The current has no effect on the welded metal, its 
action being to heat the metal. The copper clamping dies are good 
conductors, and a bar of iron, being comparatively a poor conductor, 
when placed between the clamping dies of the welder becomes 
heated in attempting to carry the large volume of current. The 
degree of heat depending upon the amount of current and resistance 
of the conductor when the ends of the two pieces of bar are brought 
together, this is the point of the greatest resistance in the electric 
circuit, and the abutting ends heat most rapidly. 

Production will depend largely on the operator, the size and 
shape of the piece to be welded, and the kind of machine used. 
There is a wide range in the time between the heavy pieces and the 
light pieces which can be handled rapidly and easily. Some of the 
smaller machines deal with several thousands of pieces a day, and 
to get the maximum output the best machines should be adopted. 
The welding machine can be used on one phase of a three-phase 
system, but cannot be connected to more than one phase of a three- 
phase circuit. Direct current cannot be used, because there is no 
way of reducing the voltage without interposing resistance, which 
uses up the power. The voltage used at the weld is from 1 to 15, 
depending on the size of the welding machine. To obtain this 
low voltage or pressure, a special transformer inside the machine 
reduces the power line voltage down to the range. It is like 
reducing steam pressure from 100 to 10 pounds. 

The welding transformer which produces the heavy current across 
the work is supported with the frame. Single-phase alternating 
current is taken from a generator, or power circuit, and is stepped 



238 MODERN METHODS OE WELDING 

down by the transformer to a low potential of from 1 to 15 volts. The 
secondary winding of the transformer is connected to the platens, 
and the current travels through the platens, clamps, and metals 
to be welded, thereby completing an electric circuit. Since the 
current value rises as the potential falls in the secondary circuit, 
and since also the heating effect across the work is directly propor- 
tioned to the current value, it is easily seen why a transformer is 
necessary to produce a heavy current by lowering the time potential. 
Owing to the intermittent character of the load, there is no standard 
rating for welder transformers. Different makers will give entirely 
different ratings for their machines, and not infrequently make 
misleading statements regarding the current used. Regardless of 
the rating in k.w. capacity, there can be very little difference in the 
actual amount of current consumed unless an exceptionally bad 
transformer design is used. To heat a given size stock to the 
welding temperature in a given time requires approximately an 
invariable amount of current. 

The following illustration shows a machine for welding tool steel. 
In any tool welding there are different kinds of welds to be made, 
which require different classes of dies and two different types of 
machines. We will first deal with the class of work which comes 
under reamers, milling and key-way cutters with taper shanks, 
and other similar make-up. The high speed and the carbon steel 
pieces should be prepared to secure the best results on a production 
basis. When making this style of tool the dies should be specially 
prepared to do the work. Since the high-speed steel has a higher 
resistance than the carbon steel it has a great tendency to reach the 
plastic stage of heat sooner than the latter. Eor this reason it should 
have a shorter projection beyond the dies to secure still greater 
cooling effect and to retard its heating as much as possible. 

Thorough tests have been made on the strength of electrically 
welded bars which prove that they are almost as strong at the welded 
joint as at any other cross-section of the metal. When welding in a 
forge, the outer surface is heated first, and the inner part does not 
very often reach welding heat, the result being an imperfect weld. 
The only preparation of the stock necessary for this process is that, 
when it is rusty or covered with blue scale, the rust and scale 
should be removed sufficiently to give good contact of clean metal 
at the gripping dies, as both scale and rust are poor conductors. 

The butt-welding process is applicable to the welding of pieces 
having practically the same cross-section at the joint. A very few 
seconds after the current is turned on in the welder, the metal reaches 



ELECTRIC BUTT WELDING 



239 



a white heat, and is in a partially molten state. By means of heavy 
pressure the ends of the metal are forced into each other in this semi- 




Fig. 116. — Butt-Welding Tool Steel to Mild Steel Bars. 



fluid condition, extruding all burnt metal, thus making a homogene- 
ous mass and a perfect weld. A projection or fin will be raised where 
the ends come together, by the squeezing out of the burnt metal, 



240 MODERN METHODS OF WELDING 

which may be very slight on an "upset," or quite a fin may be 
raised in a flash weld. Both are shown below. 

Butt Electric Welding Process. — The parts to be welded are 
brought into contact under pressure and then a current of high 
amperage under low voltage is passed from one part through the 
joint to the other part. Because of the high resistance at the con- 
tact areas, the metal at the joint is quickly brought to a welding 
heat, when the plasticity of the metal allows the pressure to cause 
movements of the two parts towards each other. Under the combined 
temperature and pressure the parts are welded, much as welding 
is done under the blacksmith's hammer — perhaps, above all, in 
that the heating and welding operations are performed practically 
at the same time and almost instantaneously. As soon as the weld- 
ing heat is reached the welding is immediately effected. In the 
lighter kind of work the rapidity with which this heat is attained is 




Fig. 117.— Butt Weld. Right, Flash Weld; Left, Upset Weld. 

quite remarkable. Although the process is not applicable to every 
form of welding, yet the sphere of its utility is very wide, and 
the quality of the work effected by it is unquestionably good. 
It is necessary for its effective operation to have at command heavy 
flows of current, but, on the other hand, the voltage is very low. 
In some cases as low an electromotive force as half a volt is all that 
is required. In actual practice from 4 to 6 volts is about the highest 
pressure worked with. The temperature of the metal to be welded 
is raised simply by a very heavy current flowing through a restricted 
area. The British Insulated and Helsby Cables, Ltd., make a large 
variety of these machines for electric welding on the resistance 
system. The electric arrangements involved in all machines are 
fundamentally the same as those employed in all systems of resist- 
ance welding — that is to say, each machine embodies a transformer, 
wound so as to perform the particular work desired under the con- 
ditions of voltage and periodicity of the supply current available. 
The secondary coil of the transformer consists of a single convo- 
lution, having a large cross-section of copper, which terminates ex- 



ELECTRIC BUTT WELDING 



241 



ternally in the two electrodes, which are of various forms. The pieces 
to be welded are brought between these two electrodes, thus com- 
pleting the electrical circuit of the secondary coil, so tr at when the 
primary circuit is closed a heavy current flows in the former, as the 
resistance to the flow of that current is practically all centred in the 
surfaces in contact. Since the ohmic resistance of the secondary 




Fig. 118. — Butt Welder for Tool Steel and Other Work. 



winding is comparatively negligible, great heat is developed between 
the electrodes, and the material between them is cpiickly brought up 
to a welding temperature. 

Attention may be drawn to the various types of butt-welding 
machines to suit different purposes: (1) Welders for wire with auto- 
matic upsetting gear for uniform section iron, steel, or non-ferrous 

16 



242 



MODERN METHODS OF WELDING 



metals; (2) welders for manufacturing purposes with hand or auto- 
matic upsetting gear for regular sections; (3) chain welders. 

Wire welders is the term which applies to the machine in No. I, 
some capable of welding 0-024 diameter. Larger machines of this 
type are able to weld material up to 1 inch square. The machines 
in the second category are used for such manufacturing purposes, 
amongst a host of others, as welding pipe refrigerator-coils, milk-can 
rings, perambulator rings, printers' chases, fittings to casement 



t^2^gSjK& r "-if X '"- ' '"^^SSHlMfi 




Fig. 119. — Butt Welder making Chains Automatically. 



frames, carriage and coach work parts, trellis work, coupling links, 
brake rigging, travelling-bag frames, low-grade shanks on high-speed 
tools, drills, taps, etc. 

The chain welders form a class by themselves, though the general 
principles involved are very much the same as those of other 
machines. The manufacture is carried out from coils of wire by two 
machines, the first of which bends the links and threads them into a 
chain, whilst the second forms the welds. Although the first machine 
is not shown in this book, it is necessary to describe it, since the 



ELECTRIC BUTT WELDING 243 

complete process cannot be properly understood without it. Three 
machines are made which deal with wires from /^ to ■£$ inch. The 
smallest machine turns out 50 to 60 links per minute and takes 
1 to 2| horse-power to drive it. The middle size turns out 40 to 50 
per minute, and requires 2 to 4 horse-power to drive it. The large 
one makes from 20 to 30 links per minute, and the horse-power 
needed is 3 to 7. The minimum proportions of the links made on 
these machines are — -length 5 diameters and width 3 diameters 
of wire. 

General Information. — The material to be welded should be ground 
or filed flat and square at the abutting ends, otherwise accurate 
results cannot be obtained. The wires to be joined are each gripped 
in a vice and the two ends projecting equally; one of the vices is 
movable and the other fixed. While the machine is being set up a 
spring pressure is taken up by a pawl engaging with a rack. While 
welding, the pawl is disengaged, and this pressure is transmitted to 
the joint. As long as the wires are cold the side remains stationary, 
but as soon as the current is sent through they soften and give way : 
the weld is jumped as soon as the required temperature is reached, 
and simultaneously the current is cut off, nothing further taking 
place. 

The illustration on the opposite page is of a chain welder, which 
has been described previously. 



CHAPTER XXXVII 

ELECTRIC SEAM WELDING 

Seam welding is a process of joining two overlapping edges of sheet 
metal for their entire length by perfect cohesion of the molecules 
of the material itself, without the application of any solder or spelter 
between the edges of the joint. In the process of seam welding the 
heat is produced by passing a large volume of electric current across 
the joint of the edges to be welded by the employment of a copper 
roller on one side of the joint, a copper track or horn underneath. 
In any electrical path, wherever high resistance is interposed, heat- 
ing will result. The higher the resistance to the current the greater 
will be the heating effect. In seam-welding machines, since the 
copper rollers and horn are good conductors, the joint between the 
edges of the metal to be welded is the point of highest resistance, 
and it is evident that the greatest heating effect will be at this point. 
As the roller passes over the joint, heating the stock to a plastic 
state beneath it, pressure is simultaneously applied by the springs on 
the roller to force the edges together as fast as they are heated. 

Since 20-gauge metal and lighter heats very readily, the pressure 
and the heating can be effected at the same instant of contact by the 
roller. It is possible to weld as fast as 6 inches a second. The 
only preparation necessary for seam welding is that the stock must 
be absolutely clean — -that is, free from any traces of rust, scale, 
grease, or dirt — if a tight, neat joint is desired. If it is not necessary 
for the joint to be tight, the stock need not be so clean, although 
heavy rust and scale will prevent the carriage of the full current, 
the heating will be affected, and the weld Mali not be so good. 

In welding sheet brass from 22- to 30-gauge, to secure a perfect 
joint the metal should be carefully pickled and washed to remove all 
traces of grease and tarnish, which tend to prevent the passage of 
the current across the joint of the edges. The metal should be 
welded soon after pickling, as, no matter how carefully it may have 
been washed, oxidation is always sure to start very shortly after the 
brass has been removed from the pickling acid. 

Steel to be successfully seam welded should not have a carbon 

244 



ELECTRIC SEAM WELDING 



245 



content of over 0-15 per cent. A higher carbon steel than this has a 
tendency to crystallise at the point of the weld, owing to the rapid 
cooling of the welded portion from the surrounding cold metal. After 
welding, the joint will be found to be about one-third thicker than the 
thickness of the metal. It is possible by applying more pressure to 
reduce this finished thickness, but it wears more on the copper roller 
to do so. In seam welding brass, a soft, annealed metal should be 
used, for, although hard rolled brass can be welded, it forces the two 
edges together very much, and the finished joint under these con- 
ditions is almost twice the original thickness. With a soft, annealed 




Fig. 120. — Electric Seam-Welding Machine. 



brass the finished joint will not be over a third greater than the single 
metal thickness, and by applying sufficient pressure it can be reduced 
to not over 10 per cent, thicker. 

The principal advantage of the process of seam welding in brass 
and other non-ferrous metals is that no spelter or flux is required, 
nor is there any volatilisation of the zinc, the metal itself furnishing 
its own cohesive properties. This allows of great speed in production. 
The great ability of a seam welder to secure the highest production 
lies, not only in its welding qualities, but in the adaptation to the 
welding machine of a suitable jig. The jig holds the work properly, 



246 MODERN METHODS OF WELDING 

and also enables the operator to place the piece in it and remove 
the same in the shortest possible time, since the welding itself is 
very fast compared with any other method of making a continuous 
joint. 

Fig. 120 is a photograph of a seam-welding machine. The 
operation is very simple, once the machine is set up, for any given 
piece of work for which a special jig has been built. After placing 
the piece in the jig and locking it there securely, the operator de- 
presses the foot-pedal, which throws in a clutch and starts the copper 
roller across the work. By the proper setting of adjustable control- 
stops on the control rod on the top of the machine, the current is 
automatically turned on as the rollers enter on to the overlapping 
edges of the piece to be welded, and is automatically turned off when 
the roller reaches the end of the stroke. Another stop reverses the 
travel of the roller, bringing it back to its starting position. The con- 
trol stop may be adjusted to turn the current on and off at any point 
along the roller, for doing a seam shorter than the maximum of the 
welding machine. The roller stroke may also be shortened so that 
a complete cycle of operations will be accomplished in the shortest 
space of time on seams shorter than the maximum seam capacity of 
the machine. In order to keep the copper roller from overheating 
in action, water is introduced through its bronze bearings on- each 
side. This same water circulation passes also through the under 
copper horn or madrel, then through the cast copper secondary of the 
transformer, so that the machine can be operated continually — 
twenty-four hours a day if desired — without overheating. 

Most seam-welding machines are equipped with variable- speed 
motors in order to give a range of variation in roller travel speed, 
which is necessary for different lengths and thicknesses of stock. 
They are also equipped with a current regulator to give fifty different 
voltages at the copper roller. 

To effect good sliding contact with copper track, several springs 
are employed on each side of this slide, which carries the copper 
rollers. The lower horn is bolted directly to the lower terminal of 
the transformer secondary. .The particular design in each case will 
depend upon the size and the nature of the work. 



CHAPTER XXXVIII 
EYE-PROTECTION IN IRON WELDING OPERATIONS 

In welding operations three kinds of radiations must be guarded 
against, one or all of which may be present to an injurious degree. 
The problem is to j)rovide a perfectly safe filter that will permit of 
the greatest degree of visibility, and at the same time will exclude 
the infra-red, or heat, rays and the ultra-violet rays. Ordinary glass 
lenses of special colours or combinations of colours are required. 
I show the spectra of a number of commercially available glasses and 
combinations of these glasses, and a glance at these charts will 
show what arrangement of filter will provide the best protection 
against the radiations of the welding arc. 

Radiation from an intensely heated solid or vapour may be 
divided under the headings: (1) Invisible infra-red rays; (2) visible 
light rays; (3) invisible ultra-violet rays. 

There is no clear line of demarcation between these divisions, 
as they melt gradually one into the other like the colours of the 
visible spectrum. When the heated matter is solid, such as the 
filament of an incandescent lamp, the visible spectrum is usually 
continuous — -that is, without lines or bands, but when it is in the form 
of gas or vapour, as in the iron arc used for welding operations, the 
spectrum is divided up into bands, or is crossed by lines which are 
characteristic of the element heated. 

In Fig. 121 A shows the continuous spectrum made by the light of 
a Mazda lamp operated at normal voltage, and is the line of spectrum 
made by a disruptive arc between iron terminals. 

If A and B (Fig. 121) were coloured they would show all the hues 
of the prismatic spectrum from red at the left to violet at the right, 
as roughly indicated by the vertical dividing lines. The iron spec- 
trum B falls a little short of the continuous spectrum A in the red, 
but it is more intense than A in the visible blue and violet, and it 
also extends farther into the ultra-violet. The spectrum B contains 
many lines besides those pertaining to iron, principally those of 
carbon, nitrogen, and oxygen, these elements being unavoidable 
components of the electric spark discharge. Inspection of A and B, 
however, will serve to indicate the extent and general characteristics 

247 



248 



MODERN METHODS OF WELDING 



of the visible light that is emitted by highly treated iron vapour 
in the process of arc welding. 

The radiations under the foregoing three headings, although of 






vioiet 



Ultra 
Violet 




Fig. 121. — Spectrum of a Mazda Lamp; Spectrum op Iron Arc. 

common origin, produce very diverse effects upon our senses. Thus, 
the infra-red rays produce the sensation of heat when they fall on our 
unprotected skin, and, therefore, special glasses are required to pro- 
tect the operator from their harmful effects. 




Fig. 122. — Pfund Gold Glass Goggles. 



For welding with acetylene and for light electric welding it 
may be necessary only to protect the eyes with goggles fitted with 
suitable coloured glasses. Fig. 122 shows a good form of goggles 



EYE-PROTECTION IN IRON WELDING OPERATIONS 249 

which are fitted with lenses of pfund gold glass to which reference 
will be made later. 

Fig. 124 illustrates the front and back views of a hand shield, 
which is made of light wood and has a safety coloured glass window 
in the centre. This device is used for medium weight electric welding 
work which can be done with one hand, and it serves the double 
purpose of protecting the eyes of the operator and shielding his face 
from the heat rays and the ultra-violet radiation which would other- 
wise cause a severe sunburn effect. 

For heavy electric welding which requires the use of both hands 
it is common practice for the operator to protect his eyes and neck 



1 


^POTHpPV 






>-• .. • ") 


■ 


1 




"^B 



Fig. 123. — A Popular Form of Helmet with Circular Window. 



with a helmet fitted with a round or triangular window of safety 
glass. These helmets are usually made of some strong, light material 
such as vulcanised fibre and are designed so that they can be slipped 
on and off easily, the weight resting upon the shoulders of the opera- 
tor. A useful form of helmet with a circular window is shown in 
Fig. 123. Front and back views of another form of helmet are seen 
in Fig. 125. 

It therefore naturally follows that a much clearer definition of 
an object is obtained by combination of yellow-green light than by 
red alone, or especially by blue or violet light alone. The eye is 
also more sensitive to the yellow and green rays than to the red and 



250 



MODERN METHODS OF WELDING 



blue rays, or, in other words, yellow-green light has the highest 
luminous efficiency. This may easily be verified by looking at a 
sunlit landscape or fleecy clouds in a blue sky through plates of 
different coloured glass. A glass of a light amber colour, slightly 
tinted with green, will clearly bring out details that are hardly 
observable without the glass, and which can be obscured entirely 
by a blue or violet glass. It is therefore obvious that, in order to 

obtain the clearest definition or 
visibility with the least amount of 
glare, the selection of the colour tint 
in safety glasses should properly be 
decided by an expert, but the depth 
of tint, or, in other words, the 
amount of obscuration, may be best 
determined by the operator himself 
owing to the individual difference 
in visual acuity which will permit 
one man to see clearly through a 
glass that would be too dark for 
another man. 

A proper selection of colour 
tints can be assisted by spectro- 
scopic examination, and the various 
spectra shown in the accompanying 
photographs are presented with this 
purpose in view. 

Fig. 126 shows different spectra 
made by transmitting the light of a 
Mazda lamp operated at normal 
voltage : C, through clear colourless 
glass; D, through ruby glass. 

The screen of clear colourless 
glass in C naturally transmits all 
the colours of the visible spectrum, 
extending from the extreme red 
to the extreme violet and penetrating slightly into the ultra-violet, 
because the latter rays, although they are not visible to the eye, 
are highly actinic, and therefore affect the photographic plate. In 
this case, however, we only see just the beginning of the ultra-violet 
spectrum, as the glass plate and the glass prism of the spectroscope 
absorb and cut off all but a few of the least refrangible ultra-violet 
rays. 




Fig. 124. — Welder's Hand Shield. 



EYE-PROTECTION IN IRON WELDING OPERATIONS 251 

The ruby glass, used as a screen in D, transmits all the red and 
orange rays with a trace of the yellow, but it absorbs and cuts out 
all other colours. 

The glass used in spectrum E is made by the Pittsburg Glass 
Company (Pa.), and is termed " Belgian pot-yellow " glass. It cuts 
off a little of the red, transmits all the orange and yellow rays and a 
portion of the green, but cuts out all the blue and violet. 

The emerald-green glass marked F is seen to transmit all the 
yellow and green, with a considerable portion of the red and orange 
and also of the blue. 

The spectrum made through the cobalt-blue glass marked G, 
shows the transmission of a band of red and a band of yellow- 




Fig. 125. — Front and Back Views of Thin Sheet Aluminium Helmet Sup- 
ported by a Head Band and Fitted with Rectangular Opening. 



green, but it is chiefly marked by its strong transmission of the blue 
and violet, and especially in its being a little more transparent to 
the ultra-violet than the colourless glass A. 

These five glasses are samples taken from actual service, but on 
account of the fact that all coloured glasses are subject to con- 
siderable variation in tint and depth of colour, caused by differences 
in chemical composition, heat treatment, etc., the spectra shown in 
Fig. 126 can be considered as only generally representative; samples 
of blue glass, for example, have been tested and found to absorb 
very much more of the red, yellow, and green than the sample 
shown in G. 

In H is seen a representative spectrum taken through a noviweld 



252 



MODERN METHODS OF WELDING 



glass (No. 6 grade), which presents an excellent colour combination 
to secure clear definition with the least amount of glare. 

It is possible to produce satisfactory colour tints for welders' 
glasses by combining plates of different coloured glass. The results 
of some of these combinations are shown in the spectra of Fig. 127, 
which were made with the same source of light as those of Fig. 126. 

In Fig. 127 J shows the full spectrum through clear colourless 
glass for comparison, the same as C in Fig. 126. 

In K we see the effect of combining yellow and blue glass (E and 
G of Fig. 126), which combination makes a fair resemblance to novi- 
weld, and is giving satisfactory service in certain work where the 
cost of noviweld prohibits its use. The tint of this combination 



Infra fed and Ve How 

f?ed lor&noe Liiv*6r*en| 



Slue and 
Violet 



Ultra 
Violet 




Fig. 126. — Sundry Spectra 6. 

E, Through "Belgian pot-yellow glass"; F, through emerald-green glass; 

G, through cobalt-blue glass; H, through No. 6 " noviweld " glass. 



is inclined rather too much to the red, and is somewhat weak in the 
yellow-green, but these defects could be largely overcome by a care- 
ful selection of the plates. 

The spectrum L in Fig. 127 results from a combination of ruby 
and emerald-green glass (D and F in Fig. 126), which has been found 
satisfactory for certain work and is now used extensively. 

The result of combining ruby and blue (D and G in Fig. 126) is 
shown by M in Fig. 127. It was formerly used to some extent, but 
is now almost universally superseded by L. 

The spectrum N was taken through a single plate of noviweld 
(No. 5 grade), which presents the elements of an ideal colour com- 



EYE-PROTECTION IN IRON WELDING OPERATIONS 253 

bination, being weak in the red while transmitting all the orange, 
yellow, and green, but totally excluding the blue and violet. 

The spectrum P was taken through a piece of amber mica having 
a little darker tint than No. 5 noviweld. Its close resemblance to 
the noviweld spectrum is remarkable, and if it were possible to 
procure a clear dark amber mica in pieces large enough to be service- 
able, this material, when protected from mechanical injury between 
plates of plain clear glass, would closely rival the noviweld. Clear 
dark amber mica of uniform tint and even cleavage is, however, 
very difficult to procure, for which reason there is no probability 
that it will ever supersede glass for protective purposes. 

In selecting coloured glasses, great care should be taken to dis- 




Fig. 127- — Sundry Spectra 7. 

card all samples that show streaks or spots, as these defects are liable 
to produce eye-strain. The glass should be uniform in colour and 
thickness throughout, and the coloured plates should be protected 
from outside injury by a thin piece of clear glass that can easily be 
renewed. 

Having considered briefly the best means for toning down the 
glaring and flickering visible light produced in the welding process, 
we may now direct some attention to the infra-red and the ultra- 
violet rays, which always accompany the visible glare. 

When the invisible infra-red rays encounter any material which 
they cannot penetrate or which is opaque to them, they are absorbed 
and changed into heat. Hence they are frequently termed heat rays. 
It is therefore very necessary to guard the eyes from these rays, and, 



254 



MODERN METHODS OF WELDING 



although they are absorbed to a certain extent by ordinary coloured 
glass, this is not sufficient protection against any intense source. 
There are, however, several kinds of glass which, although fairly 
transparent to visible light, are wonderfully efficient in absorbing 
heat. 

Corning glass G 124 J is one of those which, while it transmits 
60 to 70 per cent, visible light, cuts off about 90 per cent, of the heat- 
rays . The colour of this glass 
is pale green. The author has 
a pair of goggles fitted with 
plain lenses of this glass and 
has found them invaluable 
when operating on high-tem- 
perature work. There are, 
also, gold-fitted glasses which 
are superlatively efficient 
in absorbing and reflecting 
the infra-red heat rays. A 
sample of the " pfund gold 
glass " previously referred to 
was found by careful test to 
transmit only 0-8 per cent, 
of the heat rays generated by 
a 200-watt gas-filled tung- 
sten lamp operated at normal 
voltage, the temperature of 
the tungsten spirals being 
estimated at 2,400° C. This 
glass transmits light of a 
green colour and is much 
darker than the corning G 
124 J, so it probably passes 
not more than 20 per cent, of 
the visible rays. The novi- 
weld glasses, especially those of dark tints, are also very efficient 
shields against the infra-red rays. The effects of even low-power 
heat rays, when generated in close proximity to the eyes for a 
considerable time, are often serious, as is evidenced by the fact 
that glass-blowers who use their unprotected eyes near to hot 
gas flames of weak luminous intensity, are frequently afflicted with 
cataract, which might be positively avoided by wearing spectacles 
made with plain lenses of the G 124 J glass or its equivalent. 




Fig. 128.— Goggles: 47 H, 48 H, 49 H. 



EYE -PROTECTION IN IRON WELDING OPERATIONS 255 



Table I. indicates roughly the percentage of heat rays transmitted 
by various coloured glasses of given thickness. The source of heat 
used was a 200-watt gas-filled Mazda lamp operating at a temperature 
of about 2,400° C. Although substantially correct for the samples 
tested, they would necessarily vary somewhat for other samples 
of different thickness and degrees of coloration, so that they 
can be taken only as a general guide for comparative purposes. 

Table I. 



Kind of Glass. 


Thickness in Inches. 


Per Cent. Heat Rays 
Transmitted. 


Clear white mica 


0-004 


81 


Clear window glass 








0-102 


74 


Flashed ruby 








0-097 


69 


Belgian pot-yellow 








0-126 


50 


Cobalt-blue 








0-093 


43 


Emerald-green . . 








0-1 


36 


Dark mica 








0-007 


15 


Corning G 124 J glass . 








0-095 


10 


Dark noviweld . . 








0-096 


4 


Pfund gold plated 








0-114 


0-8 



We now come to the invisible ultra-violet rays, which are princi- 
pally to be feared, not only because they are invisible, but because, 
as previously stated, we have no organ or sense for detecting them, 
and we can only trace their existence by their effects. In all cases, 
however, when we are forewarned of their presence they are very 
easily shielded, for there are only a few substances which are trans- 
parent both to the visible light and to ultra-violet radiation. Fore- 
most among these latter substances, because it is most common, is 
clear natural quartz, or rock crystal, from which the so-called 
" pebble " spectacle lenses are made. 

Fluorite and selenite are also transparent to ultra-violet rays, 
but these crystalline minerals are rare and not in common use. 
However, a moderate thickness of ordinary clear glass, sheets 
of clear or amber mica, are opaque to these dangerous rays. As a 
case in point, it is well known that the mercury vapour lamp, when 
made with a quartz tube, is an exceedingly dangerous light to the 
eye, being a prolific source of ultra-violet radiation, so that when it is 
used for illumination it is always carefully enclosed in an outer globe 
of glass ; when the mercury vapour lamp, however, is made with 
a clear glass tube, it is a harmless if not very agreeable source of 
light, because the outer tube of clear glass is opaque to the ultra- 



256 MODERN METHODS OF WELDING 

violet rays that are generated abundantly within it by the highly 
luminous mercury vapour. 

When operating with a source of light which is known to be rich 
in ultra-violet rays, such as the iron arc in welding operations, it is 
not sufficient to guard the eyes with ordinary spectacles, because 
these invisible rays are capable of reflection just the same as visible 
light, and injury may easily ensue from slanting reflections reaching 
the eyes behind the spectacle lenses. Goggles that fit closely around 
the eyes are the only sure protection in such cases. Also, when 
using a hand shield, such as that shown in Fig. 124, the shield should 
be held close against the face and not several inches from it. 

It may here be mentioned that the ultra-violet rays, when thej 
are not masked or overpowered by intense visible light, produce 
the curious visible effect termed "fluorescence" in many natural 
and artificial compounds — that is, these rays cause certain com- 
pounds to shine with various bright characteristic colours, when 
by visible light alone they may appear pure white, or of some weak 
neutral tint. Thus, natural willemite, or zinc silicate, from certain 
localities (which may also be made artificially) shows a bright green 
colour under the light from a disruptive spark between iron terminals, 
whereas this compound is white, or nearly so, by visible light. Also, 
all compounds of salicylic acid, such as the sodium salicylate tablets 
which may be bought at any drug store, are pure white when seen 
by visible light, but show a beautiful blue fluorescence under ultra- 
violet rays. Many other chemical compounds could be mentioned 
which possess this curious property, but the above substances will 
suffice to illustrate the effect of fluorescence produced by ultra- 
violet rays and by which these rays may be detected. It must, 
however, be noted that these substances will only show their fluores- 
cent colours very faintly when viewed by the light of low-tension iron 
arc used in welding, because the intense light of this arc will over- 
power the weaker effect of the invisible ultra-violet rays. The true 
beauty of fluorescent colours can only be seen under a high-tension 
disruptive discharge between iron terminals, the invisible light in 
this case being weak while the ultra-violet rays are comparatively 
intense. 

Summarising the effects of means for eye-protection against 
various harmful radiations, particularly associated with welding 
operations : 

(1) The intense glare and flickering of the visible rays should be 
softened and toned down by suitable coloured glasses selected by 
an expert and having a depth of coloration which shows the clearest 



EYE-PROTECTION IN IRON WELDING OPERATIONS 257 



definition combined with sufficient obscuration of glare, which last 
feature can best be determined by the individual operator. 

(2) When infra-red rays are present to a dangerous degree a 
tested heat-absorbing or heat-reflecting glass should be employed, 
either in combination with a suitable dark-coloured glass, when a 
glaring visible light is present, or by itself in cases where the visible 
rays are not injuriously intense. 

(3) In guarding the eye from dangerous ultra-violet rays it must 
be noted carefully that "peb- 
ble " lenses are made from 
clear quartz, or natural rock 
crystal, and this material, be- 
ing transparent to these rays, 
offers no protection against 
their harmful features. On 
the other hand, ordinary 
clear glass is a protection 
against these rays when they 
are not very intense, but 
dark amber or dark amber- 
green glasses are absolutely 
protective. Glasses showing 
blue or violet tints should 
be avoided except in certain 
combinations wherein they 
may be used to obscure other 
colours. 

No. 47 H goggles are light, 
rust-proof, sanitary, strong, 
and perfectly fitting. They are fitted with essentialite amber- 
coloured lenses which afford full protection to the eyes and cover- 
glasses which protect coloured lenses. 

No. 48 H goggles have the wire shield and other metal parts 
covered with chamois ; nose-piece is soft leather. 

No. 49 H goggles have aluminium frame, are very light in 
weight, and are exceedingly popular with welders. 

No. 65 H spectacles have a nickelled steel frame and flexible 
ear-holds. Fitted with amber lenses, they are very light and com- 
fortable to wear. 

No. 76 H spectacles are fitted with essentialite amber lenses, 
have flexible ear-holds and light fibre frame, making them very 
popular with welders doing light work. 

17 




Fig. 129.— Goggles: 65 H, 76 H. 



CHAPTER XXXIX 
MIRROR WELDING 

Mirror welding is used in some of those rare cases where breaks and 
fracture occur in inaccessible places, in which ordinary methods 
could not be adopted. This method is quite a new one, and not 
known to many, and it is useful in many cases where dismantling 
would have to take place in ordinary welding. It is used where the 
space between the article for welding and the obstructing surface 
is too small. 

The operator is not able to get between the two surfaces, nor 
could the article be turned. Sometimes two or three mirrors are 
used together, and set at different angles, so as to facilitate ease in 
welding, and this adjustment has to be made very accurately so that 
the operator can do the welding with ease, with the welding line 
always in view. It is very important that the operator has every- 
thing in proper order and in the exact position for welding, 'so that 
during the welding there should be no stopping. 

It may occur in some instances where the welding has to be done 
in higher places than ordinary ones. Precautions must therefore 
be taken to secure stability of the structure used. 

In most cases of mirror welding, dissolved acetylene compressed 
in cylinders (the same as oxygen) is used. Usually these repairs 
are far from the factory, and in places where an acetylene generator 
would not be allowed. In case the dissolved acetylene is used, an 
acetylene regulator would be required for the acetylene cylinder. 
These acetylene regulators have a left-hand screw at the coupling, 
and the regulator is painted red, so as to distinguish them from the 
oxygen regulators (painted black). 

The operator must study carefully the whole job that he has 
in hand, seeing whether it is necessary to preheat the article and 
to guard against unequal and invisible stresses and strains. See 
if the metal is \ inch thick or over ; if so, it must be bevelled : in the 
instance which we are referring to it would be difficult to bevel. 
Hence, if a sound weld is to be made the bevelling must be accom- 
plished. It can be done by the cutting blowpipe, which, if the handle 

258 



MIRROR WELDING 



259 



of the cutter is held parallel to the pipe now being welded, and the 
cutter head pointed at 45 degrees to the point of welding, will 
bevel one side of the line of welding; the cutter should now be taken 
to the opposite side and the operation repeated. This should be 
clear of oxide before starting to weld. 

In welds of this description there must be two operators, one each 




Fig. 



130. — Showing the Principle of Mirror Welding with Specially 
Arranged Filler Rod. 



side, one using the blowpipe and the other the welding -rod. Special 
care must be taken by both operators in the finding of the correct 
point on the line of welding through the mirrors, and must not, under 
any circumstances, withdraw their visions from the mirrors until 
the welding line has been completed. 

A smaller blowpipe than usual should be used, as in all vertical 
and overhead welding the melted metal must not get overheated 



260 



MODERN METHODS OF WELDING 



or it will become too fluid, will not adhere, will fall from the weld, 
and the metal will be burnt and cause a larger space to be filled up, 
and it would be oxidised, burnt, and cinderised. 

All that is necessary is to heat as small a surface as possible, not 
more than J inch from the bevel (only heat the outer surface to 
about 1,000° C.J. Before starting to do any welding it is necessary 




Fig. 131. — Mirror as Applied to the Pipe heretofore Described. 



to see that all the equipment is in perfect order; a lighted torch 
should be tried to see for certain that it is correct for proceeding. 

The welding should be commenced at \ inch below the break or 
fracture : this will ensure that the break or fracture will not extend 
farther. Assuming that one has got all correct, and the trial is 
satisfactory, welding should now go forward, remembering that one 
must have a perfect neutral flame, neither oxidising nor carbonising, 
and the flame must be kept up for certai i while welding. An 



MIRROR WELDING 



261 



oxidising name causes adhesion, lack of penetration, oxidation, 
burnt and cindered weld, and the tests will fail. 

The welding-rod must be absolutely pure, free from phosphorus, 
sulphur, manganese, and other impurities; the size must be deter- 
mined by the thickness of the metal to be welded ; several rods should 




Fig. 132.— Internal Welding oe a Boiler, with a Mirror. 



be kept at hand before starting welding. Welding may now be 
started; the blowpipe must be kept on the particular welding line 
until such time as the bottom is melted, when the bottom is found 
at the starting-point; there should be no mistake about the line 
being continued from the bottom of the weld. 

The welding must be homogeneous, starting at the bottom as 



262 MODERN METHODS OF WELDING 

previously stated, and as soon as this is melted add welding-rod, 
previously heated, in the bevel and move the blowpipe forward 
with an elliptical sweep, keeping it close in the line of the welding ; 
do not let the white tip touch the metal, but keep it § inch from it, 
and go steadily forward, filling up the bevel uniformly with the feed- 
ing-rod until the end of the weld is reached. There must be no 
stoppage whatever, while welding the line fractured. If it is 
done quickly and filled in as the welding proceeds, with no stoppage, 
the weld will be a success — neat and strong. 

As soon as the welding is completed it is necessary that it be 
heated to 950° C. and allowed to cool slowly, free from air. 

The mirror welding of a boiler, as shown in Fig. 132, is one 
that needs every care and consideration; more so than the pipe 
job previously referred to, because a boiler has to stand very 
severe tests and strains during its working under steam. Another 
important point in these boiler cases is expansion and contrac- 
tion and the avoiding of internal and invisible strains. In the 
welding of this boiler it must first be made thoroughly clean; all 
deposited scale that has accumulated must be removed from the 
fracture and surroundings, and the line of welding must be filed 
to remove all rust, leaving it bright and smooth. 

Before welding can take place it is necessary to preheat a large 
area of the boiler internally so that the expansion and contraction 
may be spread over a larger area than the small confines of the weld. 
In this case it would be difficult to bevel the edges of the fracture; 
with the cutting blowpipe, therefore, in place of the bevelling, a size 
larger blowpipe may be used to penetrate right through the metal. 

Before preheating, it is necessary to have all equipment ready, 
the mirrors fixed temporarily and marked at the proper angle, and 
the blowpipe tried in position for welding. This preheating should 
be carried out by putting a fire inside the boiler until it reaches the 
temperature of 950° C. When this temperature is reached, immedi- 
ately put back the mirrors in place to the angle previously marked 
and commence welding without delay, and see that the temperature 
does not get below 800° C, or cracks or fractures will take place. 

The welding should be started at | inch beyond the line of weld- 
ing so as to prevent the crack or fracture extending farther than the 
present line of welding. It is not necessary to have two operators 
on a job like this. The blowpipe is to be one size larger than is 
usual for the thickness of metal being welded, and the pressure of 
oxygen to be slightly less than that stated on the blowpipe. First, 
the surroundings of the crack or fracture should be heated to about 



MIRROR WELDING 263 

1,000° C.j a little above the preheating temperature, and then start 
welding at the point previously referred to ; this point takes more 
heating than the other part of the welding line. 

There are difficulties of lack of penetration, bad joining, blow- 
holes, and interposition of oxide. Lack of penetration is a frequent 
occurrence. There is, however, no justification for this, if operators 
will only go to the bottom of the weld in all cases. Interposition 
of oxide is a common occurrence, and all operators should study 
this and make test pieces until they are satisfied that there is no 
interposition. It occurs, chiefly, with excess of oxygen and using 
too large a blowpipe. The oxide formed through these errors is im- 
prisoned in the metal. It is very important to see that during the 
welding no adhesion takes place and full penetration has been 
observed, that there is no oxidation nor blowholes, and that 
no part of the weld has been gone over twice without adding 
the welding-rod. When the welding is completed, the temperature 
should be immediately taken, and whatever it is it must be raised 
to 950° C. by putting a fire in the boiler, then allowed to cool slowly, 
free from air. When cold, test by hydraulic pressure to double 
the working pressure. 

Assuming that welding is now starting, the operator must start 
just below the fracture line, get well hot over an area of 3 x 3 inches 
before melting at the starting-point — this will increase the speed of 
welding — penetrate fully, keeping the tip of the blowpipe vertical 
and at an angle of 40 degrees, which will just suit the fracture, go 
along slowly and regularly with a gyratory movement, adding the 
necessary welding-rod, filling the fracture to its greatest extent with 
a little extra coating to give more strength ; be sure that there is no 
stoppage ; the molten metal must be semiplastic and not cinderised 
in any way, or too fluid — just at a temperature that will scarcely 
run; a good weld will then be obtained. 






PRINTED IN GREAT BRITAIN BY 
BILLING AND SONS, LTD., GUILDFORD AND ESHER 



are prepared to supply, either from 

their complete stock or at 

short notice, 

Any Technical or 

Scientific Book 

In addition to publishing a very large 
and varied number of Scientific and 
Engineering Books, D. Van Nostrand 
Company have on hand the largest 
assortment in the United States of such 
books issued by American and foreign 
. publishers. 



All inquiries are cheerfully and care- 
fully answered and complete catalogs 
sent free on request. 



8 Warren Street - - New York 



306 90 







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